Slightly speed up pip installs by skipping the version check in CI.

Also remove some old version upgrading cruft.

tox.ini

@@ -22,11 +22,9 @@ setenv =
 whitelist_externals =
     mkdir
 commands =
-    {envpython} -m pip install 'pip>=21.1.1'  # Evade CVE-2021-28363
-
-    noextra: {envpython} -m pip install {toxinidir}
-    format,perf: {envpython} -m pip install '{toxinidir}[format]'
-    format_nongpl: {envpython} -m pip install '{toxinidir}[format_nongpl]'
+    noextra: {envpython} -m pip install --disable-pip-version-check {toxinidir}
+    format,perf: {envpython} -m pip install --disable-pip-version-check '{toxinidir}[format]'
+    format_nongpl: {envpython} -m pip install --disable-pip-version-check '{toxinidir}[format_nongpl]'
 
     # Ignore the deprecation warning until pypa/setuptools#3276 is released
     tests,coverage,codecov: {envpython} -Werror -W"ignore:module 'sre_constants' is deprecated:DeprecationWarning" -m {env:MAYBE_COVERAGE:} twisted.trial {posargs:jsonschema}
@@ -69,11 +67,7 @@ commands =
 [testenv:safety]
 deps = safety
 commands =
-    {envpython} -m pip install 'pip>=21.1.1'  # Evade CVE-2021-28363
-
-    # Remove once pypa/pip#7555 is closed.
-    {envpython} -m pip install --use-feature=in-tree-build '{toxinidir}[format]'
-
+    {envpython} -m pip install --disable-pip-version-check '{toxinidir}[format]'
     {envpython} -m safety check
 
 [testenv:secrets]