gh-131418: remove unused legacy typedefs in `{md5,sha1}module.c` (#131420)

- Remove legacy typedefs `MD5_INT32` and `MD5_INT64` in `Modules/md5module.c`
- Remove legacy typedefs `SHA1_INT32` and `SHA1_INT64` in `Modules/sha1module.c`.

Those legacy typedefs were used to detect whether the host platform could
correctly implement MD5 and SHA-1, but this is no longer needed as we now
fallback to HACL* implementations.