gce: remove the language tag on instances
gce: remove the language tag on instances

The language tag is invalid for some languages (such as "c++"), since a
tag can't end with a -. Instead of somehow changing the tags to be
valid, I removed the language tag, since I'm not sure why it's useful.

Acidburn0zzz/worker,solarce/worker,henrikhodne-abandoned/worker,Acidburn0zzz/worker,travis-ci/worker,henrikhodne-abandoned/worker,solarce/worker,travis-ci/worker,travis-ci/worker,Acidburn0zzz/worker,solarce/worker,henrikhodne-abandoned/worker