flag: fix headers in documentation, again
flag: fix headers in documentation, again

Godoc expects text after a header, not code.

Change-Id: I99f412ad15e10bf9cea0dbd19019ed6ce477736c
Reviewed-on: https://go-review.googlesource.com/117595
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

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