[Chore] - Remove unneeded string extensions

[emoncuso]

Description

This PR removes an unneeded polyfill for String.includes (compat table)

It also removes some unneeded string dependencies from the package.json

TODO only if you're a HashiCorp employee

• Backport Labels: If this fix needs to be backported, use the appropriate backport/ label that matches the desired release branch. Note that in the CE repo, the latest release branch will look like backport/x.x.x, but older release branches will be backport/ent/x.x.x+ent.
  • LTS: If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
• ENT Breakage: If this PR either 1) removes a public function OR 2) changes the signature
  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
  files.
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[github-actions]

CI Results:
All Go tests succeeded! ✅

[emoncuso]

This was the meat of the change. Removing the includes extension as it's baked into JS now.

[github-actions]

Build Results:
All builds succeeded! ✅

[Monkeychip]

🚢 note: smoke tested and enterprise test passed for me locally.