cmd/pprof: point to -h in package documentation
cmd/pprof: point to -h in package documentation

Change-Id: I820c72e31fbb6471481f4483e7f13bb8b3d5d00c
Reviewed-on: https://go-review.googlesource.com/c/go/+/396881
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Trust: Eli Bendersky‎ <e83e4a9813852caf164372e4b6bd506b7819d6ab@golang.org>
Run-TryBot: Eli Bendersky‎ <e83e4a9813852caf164372e4b6bd506b7819d6ab@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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