rustup: add pointers to $PATH config in caveats

[rami3l]

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As suggested by @MikeMcQuaid, this is PR updates the caveats section of the rustup formula to prepare for #218316.

[rami3l]

(This looks like a connection error: a caveats change shouldn't influence the CI status.)

[MikeMcQuaid]

Passing on this one @rami3l as it's not Homebrew-specific (which our caveats always should be) and we already cover this in our rust formula. Thanks anyway for the PR (and for the others!).

[rami3l]

Passing on this one @rami3l as it's not Homebrew-specific (which our caveats always should be) and we already cover this in our rust formula. Thanks anyway for the PR (and for the others!).

@MikeMcQuaid I'm sorry, but I believe your suggestion for rust caveats was to consult brew info rustup so this PR should be merged before that one... I think there might be a misunderstanding going on here.

[MikeMcQuaid]

@rami3l Apologies. Can this be reworded to be a bit more specific to Homebrew's rust instead?

[rami3l]

@MikeMcQuaid I'm sorry, but due to a problematic Git operation from my side I cannot open this PR again. Would you mind having a look at #220021?