cmd/pprof: update vendored github.com/google/pprof

cmd/pprof: update vendored github.com/google/pprof

Pull in the latest published version of github.com/google/pprof
as part of go.dev/issue/36905.

Done with:

	go get github.com/google/pprof@upgrade
	go mod tidy
	go mod vendor

For #36905.

Change-Id: I3c8279fce2f20cb940a4e46b2b850703e1fc7964
Reviewed-on: https://go-review.googlesource.com/c/go/+/406359
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>