doc: fix bad link in go1.9 release notes
doc: fix bad link in go1.9 release notes

Change-Id: I64ba37428f5cc560f0f20fe039feaecf5fcda93e
Reviewed-on: https://go-review.googlesource.com/53330
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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