bpo-35967: Make test_platform.test_uname_processor more lenient to satisfy build bots.

[jaraco]

In GH-12824, I added a test to capture the status quo expectation of platform.uname.processor. Then sir bedevere informed me that the buildbots are failing. This patch is intended to address that failure.

https://bugs.python.org/issue35967

[aeros]

Thanks for the PR @jaraco. I would suggest updating the title of the PR to refer to the specific test being changed, e.g. Make test_platform.test_uname_processor .... I also have a couple of minor suggestions regarding the test itself.

[aeros]

Also, I didn't look through all of the buildbot failures, but my results above are consistent with the raspbian failure:

======================================================================
FAIL: test_uname_processor (test.test_platform.PlatformTest)
On some systems, the processor must match the output
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/var/lib/buildbot/workers/3.x.gps-raspbian/build/Lib/test/test_platform.py", line 172, in test_uname_processor
    self.assertEqual(
AssertionError: '' != 'unknown'

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @gpshead for commit d1fe7ee 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[jaraco]

If you want to schedule another build, you need to add the "🔨 test-with-buildbots" label again.

TIL

[jaraco]

It seems to me the remaining buildbot failures were due to spurious failures unrelated to this change, so I'm pretty sure this change works.