Docs for `cc_test` should mention that the `linkstatic` default is different on macOS

### Description of the bug:

The [docs for `linkstatic`](https://bazel.build/reference/be/c-cpp#cc_test.linkstatic) say that the default is `linkstatic = False` for `cc_test` targets. This isn't true on macOS because the osx toolchain does not provide a `supports_dynamic_linker` feature, which is required for `linkstatic = False` support. See https://github.com/bazelbuild/bazel/commit/ec5553352f2f661d39ac4cf665dd9b3c779e614c and https://github.com/bazelbuild/bazel/issues/4341#issuecomment-758028203 for background.

### What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

n/a, docs bug

### Which operating system are you running Bazel on?

macOS

### What is the output of `bazel info release`?

release 5.2.0

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse master; git rev-parse HEAD` ?

_No response_

### Have you found anything relevant by searching the web?

https://github.com/bazelbuild/bazel/commit/ec5553352f2f661d39ac4cf665dd9b3c779e614c
https://github.com/bazelbuild/bazel/issues/4341#issuecomment-758028203
https://bazelbuild.slack.com/archives/CGA9QFQ8H/p1665782748672499

### Any other information, logs, or outputs that you want to share?

_No response_

Start with the linked Bazel `cc_test.linkstatic` documentation and review the referenced commit and issue comment for the platform-specific behavior. Update the documentation to state that macOS has a different default, and consider the change done when the documented default matches the actual macOS toolchain behavior.

Written by the indexing model from the issue text.