cmd/vendor: update vendored github.com/google/pprof for Go 1.20 release

cmd/vendor: update vendored github.com/google/pprof for Go 1.20 release

The Go 1.20 code freeze has recently started. This is a time to
update the vendored copy.

Done by
	cd GOROOT/src/cmd
	go get -d github.com/google/pprof@latest
	go mod tidy
	go mod vendor

For #36905.

Change-Id: Iaec604c66ea8f4b7638a31bdb77d6dd56966e38a
Reviewed-on: https://go-review.googlesource.com/c/go/+/452815
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>