fix: fetch submodule tags before checking webrtc release tag

[czerwiukk]

Motivation and Context

check:webrtc-published fails on CI but passes locally

  check-webrtc-published.mjs runs git -C packages/react-native-webrtc describe --exact-match --tags HEAD. That only works if the submodule's tags are present in .git.

  - Locally it passes because the dev has previously fetched the submodule's tags.
  - On GH Actions actions/checkout@v4 with submodules: recursive checks out the submodule at the pinned SHA but does not fetch its tags, so git describe finds nothing → "Submodule HEAD (6b994c0) is not at a tagged release".

Documentation impact

• Documentation update required
• Documentation updated in another PR
• No documentation update required

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)