runtime/pprof: fix resource leak in documentation
runtime/pprof: fix resource leak in documentation

Fixes #26970

Change-Id: I0f2695434a53550cf84f702e9d8d02a37448d396
Reviewed-on: https://go-review.googlesource.com/129195
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

akutz/go,golang/go,nawawi/go,cloudflare/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,CAFxX/go,josharian/go,akutz/go,josharian/go,cloudflare/go,josharian/go,cloudflare/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,cloudflare/go,josharian/go,akutz/go,cloudflare/go,golang/go,nawawi/go,josharian/go,golang/go,akutz/go,cloudflare/go,golang/go,josharian/go,nawawi/go,nawawi/go,akutz/go,josharian/go,akutz/go,akutz/go,CAFxX/go,CAFxX/go,akutz/go,CAFxX/go,josharian/go,cloudflare/go,golang/go,nawawi/go,golang/go