[FIX] runbot: remove deprecated method

The refresh method is deprecated and invalidate_cache should be used
instead. Also, since the new API, the cache is automatically
invalidated, hence this removal.

runbot/models/build.py

@@ -415,7 +415,6 @@ class runbot_build(models.Model):
                 else:
                     v['job'] = jobs[jobs.index(build.job) + 1]
                 build.write(v)
-            build.refresh()
 
             # run job
             pid = None