Dropping `PyPy3.7` from `wheels-{macos,windows}`

[Radonirinaunimi]

The CI release has failed because the previously used macos runners have reached EOL. I updated them to use macos-15 but then PyPy 3.7 is no longer available in aarch64 macos.

I believe there isn't other way than dropping this?

[felixhekhorn]

I don't think so; 3.7 has reached end-of-life ~3 years ago; I had to drop 3.9 from eko NNPDF/eko#490 as it was no longer supported in our CIs

[cschwan]

I've opened #374 mainly to see whether MacOS 14 would help solve the problem, but I'm getting:

The job was not started because recent account payments have failed or your spending limit needs to be increased. Please check the 'Billing & plans' section in your settings

[cschwan]

Normally, I'd be strongly against this when releasing a patch version, but:

• it seems we only support PyPy for MacOS, according to PyPI
• even though PyPy 3.7 was enabled for MacOS, I can't find a wheel here: https://pypi.org/project/pineappl/#files
• instead we support PyPy 3.11 (?), which we didn't enable
• the Python CLI packages also don't seem to be affected by the selected Python version, see here: https://pypi.org/project/pineappl-cli/1.3.0/#files

This leads me to believe the Python version selection simply doesn't work (see #323) and consequently I'm in favour of removing code that doesn't work.