Exclude _testclinic_depr.c.h from c-analyzer (GH-137086)

_testclinic.c mocks out PY_VERSION_HEX to 3.8 before including
_testclinic_depr.c.h to avoid the errors the preprocessor would
otherwise throw due to the deprecation feature it is testing.

Also partially revert 74e2acddf68b31ce16e8e0067b1df8c7b67bd6c8:
this restores Modules/_testclinic.c to match the same file in the 3.14
branch.