Bug 1357753: Fix try branch name. r=jlund

"Try" with capital T is causing bustage with Taskcluster test jobs.

MozReview-Commit-ID: BNNW4nFf0Ro

taskcluster/taskgraph/transforms/tests.py

@@ -457,7 +457,7 @@ def setup_talos(config, tests):
         # name is only required for try
         if config.params['project'] == 'try':
             extra_options.append('--branch-name')
-            extra_options.append('Try')
+            extra_options.append('try')
 
         yield test