Convert manually triggered try runs to use bots without _swarming prefix.

chrome/browser/policy/PRESUBMIT.py

Index: chrome/browser/policy/PRESUBMIT.py
diff --git a/chrome/browser/policy/PRESUBMIT.py b/chrome/browser/policy/PRESUBMIT.py
index 0de11cae1b1a439cf34d0b8abdd07381740897ef..ea93f85a5d894f7b73aafc3d193023d6c7d0c5cb 100644
--- a/chrome/browser/policy/PRESUBMIT.py
+++ b/chrome/browser/policy/PRESUBMIT.py
@@ -11,7 +11,7 @@ for more details on the presubmit API built into gcl.
 def GetPreferredTryMasters(project, change):
   return {
     'tryserver.chromium.linux': {
-      'linux_chromium_chromeos_rel_swarming': set(['defaulttests']),
+      'linux_chromium_chromeos_rel': set(['defaulttests']),
       'linux_chromium_chromeos_clang_dbg': set(['defaulttests']),
     }
   }