Drop cpy3.8 and 3.13t.

[mdavidsaver]

cpy 3.8 and 3.13t have been dropped from from manylinux images pypa/manylinux#1882.

epicscorelibs/.github/workflows/build.yml

Lines 29 to 30 in a7c0442

	- ml: manylinux2014_x86_64
	py: cp38-cp38

epicscorelibs/.github/workflows/build.yml

Lines 47 to 48 in a7c0442

	- ml: manylinux2014_x86_64
	py: cp313-cp313t

[mdavidsaver]

And it looks like support for manylinux2014 will end in ~1 year. pypa/manylinux#1925

[mdavidsaver]

py3.8 is still available on the manylinux2010 image. Since it would seem odd to provide py3.7 and not 3.8, I propose to "regress" the 3.8 builds to 2010 for the next set of releases (for those packages still supporting back to 3.8).

[mdavidsaver]

Right, I belatedly remember that py3.7 wheels are being built, but no longer uploaded since #46.

Is it worth the trouble of potential ml2010 vs. 2014 ABI issues to continue to provide wheels for py3.8?