Removed unused field from CQ config

testing/commit_queue/config.json

 {
     "commit_burst_delay": 60,
     "commit_user": "commit-bot@chromium.org",
     "cq_status_url": "https://chromium-cq-status.appspot.com",
     "git_repo_url": "https://chromium.googlesource.com/chromium/src",
     "hide_ref_in_committed_msg": true,
     "max_commit_burst": 2,
     "project_bases_legacy": [
         "^svn\\:\\/\\/svn\\.chromium\\.org\\/chrome/trunk/src(|/.*)$",
         "^svn\\:\\/\\/chrome\\-svn\\/chrome/trunk/src(|/.*)$",
         "^svn\\:\\/\\/chrome\\-svn\\.corp\\/chrome/trunk/src(|/.*)$",
         "^svn\\:\\/\\/chrome\\-svn\\.corp\\.google\\.com\\/chrome/trunk/src(|/.*)$",
         "^http\\:\\/\\/src\\.chromium\\.org\\/svn/trunk/src(|/.*)$",
         "^https\\:\\/\\/src\\.chromium\\.org\\/svn/trunk/src(|/.*)$",
         "^http\\:\\/\\/src\\.chromium\\.org\\/chrome/trunk/src(|/.*)$",
         "^https\\:\\/\\/src\\.chromium\\.org\\/chrome/trunk/src(|/.*)$"
     ],
     "project_bases_legacy_from_git_repo_url": true,
     "remote_branch": "refs/pending/heads/master",
     "rietveld_url": "https://codereview.chromium.org",
     "rietveld_user": "commit-bot@chromium.org",
     "skip_throttle_users": [
         "commit-bot@chromium.org"
     ],
-    "tryserver_url": "http://build.chromium.org/p/tryserver.chromium/",
     "use_buildbucket_for_tryjobs": true,
     "verifiers_no_patch": {
         "experimental_try_job_verifier": {
             "10 percent experiment": {
                 "percentage": 0.1,
                 "trybots": {
                     "launched": {
                         "tryserver.chromium.linux": {
                             "android_amp_rel_tests_recipe": [
                                 "defaulttests"
@@ skipping 139 matching lines @@
                         "defaulttests"
                     ],
                     "win_chromium_x64_rel_ng": [
                         "defaulttests"
                     ]
                 }
             }
         }
     },
     "version": 1
-}
+}