[dcmtk] re-enable support on arm64-osx

[kevle]

Describe the pull request

• What does your PR fix?

  Re-enables dcmtk build on arm64-osx

• Which triplets are supported/not supported? Have you updated the CI baseline?

  arm64-osx is a community triplet and not applicable to ci.baseline.txt from what I can tell.
  arm64-windows and arm-uwp still fail in CI, so support has been excluded for those in the port file
  arm[64]-{android,ios,linux,mingw} etc. are untested, I might be able to test crosscompilation for arm[64]-linux if that is necessary
  Since #23034 explicitly references arm mac, I think this should be ok.

• Does your PR follow the maintainer guide?

  Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

  Yes

[kevle]

@microsoft-github-policy-service agree

[BillyONeal]

Thanks!

[BillyONeal]

• Since #23034 explicitly references arm mac, I think this should be ok.

That says that it does not work on arm mac. However it also removed entries from ci.baseline.txt and maybe that was a drive-by. I'm interpreting that you made this PR as "it works for me" so I merged it.