Link to rate limit issue in GitHub Actions remote cache provider docs…

… (Cherry-pick of #20690) (#20692)

I think #20133 is basically a blocker for serious useful usage of the
`remote_provider = "experimental-github-actions-cache"` backend, so it's
worth calling out specifically, rather than forcing users to discover
the errors and track down the issue themselves.

Co-authored-by: Huon Wilson <[email protected]>

docs/docs/using-pants/remote-caching-and-execution/remote-caching.mdx

@@ -42,7 +42,9 @@ If the endpoint is using TLS, then the `remote_store_address` option would be sp
 GitHub Actions provides a built-in caching service which Pants supports using for sharing caches across GitHub Actions runs (not with machines outside of GitHub Actions). It is typically used via the `actions/cache` action to cache whole directories and files, but Pants can use the same functionality for fine-grained caching.
 
 :::caution GitHub Actions Cache support is still experimental
-Support for this cache provider is still under development, with more refinement required. Please [let us know](/community/getting-help) if you use it and encounter errors or warnings.
+Support for this cache provider is still under development, with more refinement required. Pants' fine-grained caching makes for many requests, and thus [often hits rate limit errors](https://github.com/pantsbuild/pants/issues/20133).
+
+Please [let us know](/community/getting-help) if you use it and encounter errors or warnings.
 :::
 
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