Switch to latest git build of oauth2-proxy.
Switch to latest git build of oauth2-proxy.

The stable release still has a bug that would somethimes clobber the
auth-cookie. Since there has not been a release for a while build the
latest git version and switch to that.

Change-Id: I84b36f996dc53b414ff13144b4565c9964d60200
GitOrigin-RevId: 83fed95814756f5628261e47edf9068c7c243695

googlecloudrobotics/core,googlecloudrobotics/core,googlecloudrobotics/core