Bump base to allow build 4.15.0.0

[swamp-agr]

Dear @hvr,

• This PR is intended to allow build cryptohash-md5 with GHC 9.0 (cabal-install-3.4.0.0, base-4.15.0.0).
• As in cryptohash-sha1 there is only one call withForeignPtr and I see nothing wrong with it.
• Locally tests were passed:

  cabal v2-test
  Build profile: -w ghc-9.0.1 -O1
  In order, the following will be built (use -v for more details):
   - cryptohash-md5-0.11.101.0 (test:test-md5) (ephemeral targets)
  Preprocessing test suite 'test-md5' for cryptohash-md5-0.11.101.0..
  Building test suite 'test-md5' for cryptohash-md5-0.11.101.0..
  Running 1 test suites...
  Test suite test-md5: RUNNING...
  Test suite test-md5: PASS
  Test suite logged to:
  $HOME/cryptohash-md5/dist-newstyle/build/x86_64-osx/ghc-9.0.1/cryptohash-md5-0.11.101.0/t/test-md5/test/cryptohash-md5-0.11.101.0-test-md5.log
  1 of 1 test suites (1 of 1 test cases) passed.
  

Closes #5.

Kind regards,
@swamp-agr

[phadej]

Done as a part of #8