drop 8.1 support, add 8.5

[brettmc]

Drop 8.1 support, and let rector upgrade the codebase with 8.2 as the minimum supported version

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.29%. Comparing base (26a2a4e) to head (a001e90).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1857      +/-   ##
============================================
- Coverage     68.34%   68.29%   -0.05%     
  Complexity     3009     3009              
============================================
  Files           449      449              
  Lines          8798     8798              
============================================
- Hits           6013     6009       -4     
- Misses         2785     2789       +4     

Flag	Coverage Δ
8.2	68.26% <ø> (-0.02%)	⬇️
8.3	68.25% <ø> (-0.01%)	⬇️
8.4	68.25% <ø> (-0.02%)	⬇️
8.5	67.45% <ø> (+0.02%)	⬆️

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[brettmc]

NB that the upstream sury repo (which our developer image and shivammathur/setup-php use), doesn't have grpc yet, hence the two failures for 8.5

[cedricziel]

@brettmc rector config can also be adjusted :)

[brettmc]

rector config can also be adjusted :)

oh yeah, of course. That's an important missing step, thanks! :)

[Nevay]

Should also update CONTRIBUTING.md and Makefile.

[Nevay]

Suggested change

	php-version: ['8.2', '8.3']
	php-version: ['8.2', '8.3', '8.4']

And remove 8.4 from include below. --ignore-platform-reqs should be no longer required, the 8.4 image contains ext-grpc.