Upgrade R to 4.4.2

[rgaiacs]

[manics]

FAILED tests/unit/test_r.py::test_version_specification[-4.2] - AssertionError: assert False
 +  where False = <built-in method startswith of str object at 0x7f36265fa3f0>('4.2')
 +    where <built-in method startswith of str object at 0x7f36265fa3f0> = '4.4.2'.startswith
 +      where '4.4.2' = <repo2docker.buildpacks.r.RBuildPack object at 0x7f3626370af0>.r_version

[rgaiacs]

I will work on it in the next couple of weeks.

[rgaiacs]

This is ready to be merged.

[yuvipanda]

I've updated the PR title to indicate that this moves the default R version to 4.4 from 4.2.