CI: update-pinned-requirements is a little too fast

[woodruffw]

Defect during 2.0 release: https://github.com/sigstore/sigstore-python/actions/runs/6342972187/job/17229957076

Run cd install
  ERROR: Could not find a version that satisfies the requirement sigstore==2.0.0 (from versions: 0.0.1rc1, 0.0.1rc2, 0.0.1rc3, 0.1.0, 0.2.0, 0.3.1, 0.4.0, 0.4.1, 0.4.2, 0.5.0, 0.5.1rc1, 0.5.1rc2, 0.5.1, 0.6.1, 0.6.2, 0.6.3, 0.6.4, 0.6.5, 0.6.6, 0.6.7, 0.6.8, 0.7.0, 0.8.3, 0.9.0, 0.10.0, 1.0.0rc1, 1.0.0, 1.1.0, 1.1.1rc1, 1.1.1, 1.1.2rc1, 1.1.2, 2.0.0rc1, 2.0.0rc2, 2.0.0rc3)
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/pip/_vendor/resolvelib/resolvers.py", line 397, in resolve
    self._add_to_criteria(self.state.criteria, r, parent=None)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/pip/_vendor/resolvelib/resolvers.py", line 174, in _add_to_criteria
    raise RequirementsConflicted(criterion)
pip._vendor.resolvelib.resolvers.RequirementsConflicted: Requirements conflict: SpecifierRequirement('sigstore==2.0.0')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/pip/_internal/resolution/resolvelib/resolver.py", line 92, in resolve
    result = self._result = resolver.resolve(
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/pip/_vendor/resolvelib/resolvers.py", line 546, in resolve
    state = resolution.resolve(requirements, max_rounds=max_rounds)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/pip/_vendor/resolvelib/resolvers.py", line 399, in resolve
    raise ResolutionImpossible(e.criterion.information)
pip._vendor.resolvelib.resolvers.ResolutionImpossible: [RequirementInformation(requirement=SpecifierRequirement('sigstore==2.0.0'), parent=None)]

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.16/x64/bin/pip-compile", line 8, in <module>
    sys.exit(cli())
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/click/decorators.py", line [33](https://github.com/sigstore/sigstore-python/actions/runs/6342972187/job/17229957076#step:9:34), in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/piptools/scripts/compile.py", line 659, in cli
    results = resolver.resolve(max_rounds=max_rounds)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/piptools/resolver.py", line 604, in resolve
    is_resolved = self._do_resolve(
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/piptools/resolver.py", line 6[36](https://github.com/sigstore/sigstore-python/actions/runs/6342972187/job/17229957076#step:9:37), in _do_resolve
    resolver.resolve(
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/pip/_internal/resolution/resolvelib/resolver.py", line 101, in resolve
    raise error from e
pip._internal.exceptions.DistributionNotFound: No matching distribution found for sigstore==2.0.0
Error: Process completed with exit code 1.

TL;DR is that we run this workflow right after successful PyPI publish, which means that PyPI may not actually be serving the new release just yet.

Possible resolutions:

• Make this workflow manual-only, include a note in our release process reminding someone to run it
• Make the workflow poll PyPI for the new version, and only continue once present
• Make the workflow wait for 1-2 minutes before attempting to do anything (the lazy way)