Confusing documentation on recommended race detector usage

### What version of rules_go are you using?

v0.22.1

### What did you do?

I'm just trying to understand the recommended usage for the race detector and `go_test`.

### What did you expect to see?

Consistent documentation and or an explanation behind the recommended usage.

### What did you see instead?

The "Using the race detector" subsection of `modes.rst` recommends the following in regards to using the race detector globally:

> but in general it is strongly recommended instead to turn it on for specific tests

https://github.com/bazelbuild/rules_go/blob/v0.22.1/go/modes.rst#using-the-race-detector

However the `core.rst` documentation for `go_test` race attribute has the following:

> In most cases, it's better to enable race detection globally with --features=race on the command line.

https://github.com/bazelbuild/rules_go/blob/v0.22.1/go/core.rst#go_test

So it would be nice to have an explanation for either or both recommendations.

Compare the “Using the race detector” subsection in go/modes.rst with the go_test race attribute documentation in go/core.rst. Read both recommendations and determine what explanation or wording is needed to make them consistent. Done means the documentation clearly explains when to use global versus test-specific race detection.

Written by the indexing model from the issue text.