go.tools/dashboard/app: don't ignore field mismatch errors
go.tools/dashboard/app: don't ignore field mismatch errors

This was a hold-over from when we removed install counts years ago.
All the Package entities are well-formed these days.

LGTM=dsymonds
R=dsymonds
CC=golang-codereviews
https://golang.org/cl/138620043

proppy/build,proppy/build,proppy/build,proppy/build,golang/build,golang/build,golang/build,evandbrown/build,evandbrown/build,golang/build,evandbrown/build