fix a typo in the runtime.MemStats documentation
fix a typo in the runtime.MemStats documentation

Change-Id: If553950446158cee486006ba85c3663b986008a6
Reviewed-on: https://go-review.googlesource.com/82936
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

josharian/go,Cofyc/go,josharian/go,codestation/go,CAFxX/go,codestation/go,nawawi/go,CAFxX/go,CAFxX/go,Cofyc/go,codestation/go,codestation/go,cloudflare/go,nawawi/go,codestation/go,CAFxX/go,nawawi/go,codestation/go,cloudflare/go,cloudflare/go,cloudflare/go,akutz/go,golang/go,akutz/go,codestation/go,CAFxX/go,codestation/go,Cofyc/go,CAFxX/go,Cofyc/go,nawawi/go,CAFxX/go,golang/go,josharian/go,akutz/go,CAFxX/go,nawawi/go,Cofyc/go,golang/go,josharian/go,nawawi/go,golang/go,akutz/go,Cofyc/go,cloudflare/go,cloudflare/go,cloudflare/go,akutz/go,akutz/go,nawawi/go,golang/go,nawawi/go,golang/go,golang/go,josharian/go,Cofyc/go,josharian/go,cloudflare/go,christopher-henderson/Go,josharian/go,akutz/go,Cofyc/go,akutz/go,golang/go,josharian/go