Temporarily allow Python 3.10 installations

[jrmccluskey]

Lower python_requires bounds to prevent breakages of some downstream consumers of Beam Python snapshots that have not migrated off of Python 3.10 yet (like Dataflow Notebooks nightly snapshots.) When a new release versions is cut and those consumers need to support 2.78.0 they will have to update or omit support for the version.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 56.23%. Comparing base (76f6e6d) to head (5b4c424).
⚠️ Report is 107 commits behind head on master.

Files with missing lines	Patch %	Lines
sdks/python/setup.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #40486      +/-   ##
============================================
+ Coverage     56.16%   56.23%   +0.06%     
  Complexity     2288     2288              
============================================
  Files          1124     1124              
  Lines        178336   178359      +23     
  Branches       1489     1489              
============================================
+ Hits         100170   100298     +128     
+ Misses        75645    75540     -105     
  Partials       2521     2521              

Flag	Coverage Δ
python	79.68% <0.00%> (+0.13%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.