[llvm] [GitHub] Add python 3.7 to libclang python test (PR #77219)

[Tom Stellard via llvm-commits]

tstellar wrote:

This is not working correctly.  One of the jobs always gets cancelled, because the concurrency_group defined in llvm-project-tests.yml is the same for both jobs since it is keyed on the input projects.

See https://github.com/llvm/llvm-project/actions/runs/7845680285

https://github.com/llvm/llvm-project/pull/77219