dashboard: update update script to delete Commit.PerfResult This is required to repair perf data in the datastore. Update golang/go#8930.
dashboard: update update script to delete Commit.PerfResult
This is required to repair perf data in the datastore.
Update golang/go#8930.

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/158320043

argandas/tools,nicot/tools,cmars/tools,golang/tools,maddyonline/tools,syreclabs/go-tools,4ad/tools,sshetty10/tools,glasser/golang-tools,cw2018/tools,jdhenke/tools,maddyonline/tools,maddyonline/tools,dmitris/tools,runcom/tools,jdhenke/tools,matryer/tools,runcom/tools,glasser/golang-tools,jdhenke/tools,syreclabs/go-tools,sshetty10/tools,syreclabs/go-tools,springning/tools,dmitris/tools,golang/tools,syreclabs/go-tools,cw2018/tools,cw2018/tools,magiccao/tools,matryer/tools,glasser/golang-tools,matryer/tools,cmars/tools,maddyonline/tools,argandas/tools,sshetty10/tools,josharian/tools,nicot/tools,matryer/tools,jdhenke/tools,nicot/tools,josharian/tools,glasser/golang-tools,runcom/tools,magiccao/tools,syreclabs/go-tools,argandas/tools,magiccao/tools,springning/tools,springning/tools,josharian/tools,nicot/tools,runcom/tools,sshetty10/tools,josharian/tools,magiccao/tools,syreclabs/go-tools,4ad/tools,golang/tools,cmars/tools,springning/tools,golang/tools,golang/tools,cmars/tools,dmitris/tools,4ad/tools,argandas/tools,cw2018/tools,dmitris/tools