cmd/godoc: exclude TestTypeAnalysis on Plan 9 for now
cmd/godoc: exclude TestTypeAnalysis on Plan 9 for now

Attempt to make build work on Plan 9.

For golang/go#11811.

Change-Id: I37a5eaef441262342994a8f77c86aa5e120deea7
Reviewed-on: https://go-review.googlesource.com/13033
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

syreclabs/go-tools,josharian/tools,jdhenke/tools,argandas/tools,nicot/tools,glasser/golang-tools,josharian/tools,springning/tools,argandas/tools,syreclabs/go-tools,glasser/golang-tools,magiccao/tools,jdhenke/tools,argandas/tools,runcom/tools,golang/tools,nicot/tools,golang/tools,josharian/tools,josharian/tools,jdhenke/tools,matryer/tools,golang/tools,golang/tools,nicot/tools,cmars/tools,syreclabs/go-tools,magiccao/tools,magiccao/tools,springning/tools,springning/tools,matryer/tools,glasser/golang-tools,springning/tools,runcom/tools,runcom/tools,cmars/tools,cmars/tools,cmars/tools,argandas/tools,jdhenke/tools,cw2018/tools,syreclabs/go-tools,matryer/tools,golang/tools,cw2018/tools,glasser/golang-tools,nicot/tools,magiccao/tools,cw2018/tools,syreclabs/go-tools,matryer/tools,cw2018/tools,runcom/tools,syreclabs/go-tools