Remove custom timeout of 16min for swarmed CTS tests.

And switch to the default of 1hr.

R=aluo, jbudorick

Bug: 907899
Change-Id: I0402ee6350594b6149f9ba95f0822eed0f438b2f
Reviewed-on: https://chromium-review.googlesource.com/c/1374523Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616096}

testing/buildbot/chromium.android.fyi.json

@@ -699,7 +699,6 @@
               "os": "Android"
             }
           ],
-          "hard_timeout": 960,
           "shards": 3
         }
       }

testing/buildbot/chromium.android.json

@@ -564,7 +564,6 @@
               "os": "Android"
             }
           ],
-          "hard_timeout": 960,
           "shards": 3
         }
       }

testing/buildbot/test_suites.pyl

@@ -2535,7 +2535,6 @@
     'webview_cts_tests_isolated_scripts': {
       'webview_cts_tests': {
         'swarming': {
-          'hard_timeout': 960,
           'shards': 3,
           'cipd_packages': [
             {