Allow tests to pass after 2038 (#620)

* Allow tests to pass after 2038

in openSUSE, this broke tests in python-aiosmtplib,
python-anyio, python-cheroot, python-trio when running after 2038-01-01

Background:
As part of my work on reproducible builds for openSUSE, I check that software still gives identical build results in the future.
The usual offset is +16 years, because that is how long I expect some software will be used in some places.
This showed up failing tests in our package build.
See https://reproducible-builds.org/ for why this matters.

* Switch to previous 3000 limit

* Add news entry

---------

Co-authored-by: Quentin Pradet <quentin.pradet@gmail.com>

newsfragments/620.feature.rst

@@ -0,0 +1 @@
+Set default expiry date to 3000-01-01 instead of 2038-01-01 to improve build reproducibility.

src/trustme/__init__.py

@@ -34,10 +34,7 @@
 # OpenSSL on Windows fails if you try to give it a date after
 # ~3001-01-19:
 #   https://github.com/pyca/cryptography/issues/3194
-# Some versions of cryptography on 32-bit platforms fail if you give
-# them dates after ~2038-01-19:
-#   https://github.com/pyca/cryptography/pull/4658
-DEFAULT_EXPIRY = datetime.datetime(2038, 1, 1)
+DEFAULT_EXPIRY = datetime.datetime(3000, 1, 1)
 
 def _name(name: str, organization_name: Optional[str] = None, common_name: Optional[str] = None) -> x509.Name:
     name_pieces = [