doc/go1.7.html: mention Server.Serve HTTP/2 behavior change
doc/go1.7.html: mention Server.Serve HTTP/2 behavior change

Fixes #16550
Updates #15908

Change-Id: Ic951080dbc88f96e4c00cdb3ffe24a5c03079efd
Reviewed-on: https://go-review.googlesource.com/25389
Reviewed-by: Chris Broadfoot <0c2851a4f8ab4aa5606e69c0757771dd13dbe686@golang.org>

suncycheng/go,josharian/go,goodlang/good,momchil-velikov/go,derekmarcotte/go,4ad/go,cloudflare/go,linux-on-ibm-z/go,codestation/go,momchil-velikov/go,CAFxX/go,suncycheng/go,codestation/go,akutz/go,ImJasonH/go,Cofyc/go,josharian/go,CAFxX/go,cloudflare/go,4ad/go,suncycheng/go,vsekhar/elastic-go,4ad/go,golang/go,linux-on-ibm-z/go,nawawi/go,nawawi/go,linux-on-ibm-z/go,cloudflare/go,momchil-velikov/go,CAFxX/go,vsekhar/elastic-go,golang/go,ImJasonH/go,cloudflare/go,linux-on-ibm-z/go,Cofyc/go,suncycheng/go,polyverse-security/go,derekmarcotte/go,cloudflare/go,derekmarcotte/go,derekmarcotte/go,4ad/go,ImJasonH/go,Cofyc/go,polyverse-security/go,vsekhar/elastic-go,golang/go,momchil-velikov/go,4ad/go,linux-on-ibm-z/go,4ad/go,golang/go,CAFxX/go,goodlang/good,akutz/go,momchil-velikov/go,CAFxX/go,momchil-velikov/go,golang/go,codestation/go,vsekhar/elastic-go,Cofyc/go,codestation/go,Cofyc/go,4ad/go,akutz/go,golang/go,polyverse-security/go,cloudflare/go,golang/go,CAFxX/go,linux-on-ibm-z/go,momchil-velikov/go,josharian/go,nawawi/go,nawawi/go,linux-on-ibm-z/go,akutz/go,cloudflare/go,ImJasonH/go,ImJasonH/go,suncycheng/go,ImJasonH/go,Cofyc/go,ImJasonH/go,josharian/go,goodlang/good,nawawi/go,polyverse-security/go,goodlang/good,vsekhar/elastic-go,4ad/go,polyverse-security/go,polyverse-security/go,nawawi/go,goodlang/good,cloudflare/go,derekmarcotte/go,derekmarcotte/go,akutz/go,momchil-velikov/go,akutz/go,vsekhar/elastic-go,derekmarcotte/go,nawawi/go,linux-on-ibm-z/go,josharian/go,polyverse-security/go,suncycheng/go,polyverse-security/go,codestation/go,josharian/go,akutz/go,Cofyc/go,CAFxX/go,suncycheng/go,josharian/go,josharian/go,codestation/go,derekmarcotte/go,CAFxX/go,goodlang/good,ImJasonH/go,goodlang/good,goodlang/good,suncycheng/go,Cofyc/go,christopher-henderson/Go,vsekhar/elastic-go,vsekhar/elastic-go,codestation/go,akutz/go,golang/go,codestation/go,nawawi/go