Temporarily remove mash_browser_tests from CrOS bots.

It looks like they have several issues. This removes them from
both the "Linux ChromiumOS Ozone Tests (1)" builder and the
"Linux ChromiumOS Tests (1)" builder, so it should stop breaking
the CQ builds.

TBR=jonross@chromium.org, kbr@chromium.org, qyearsley@chromium.org
NOTRY=true
BUG=742966

Change-Id: Ie96885593e40b1ff62e76dc1b09aa01d15e20529
Reviewed-on: https://chromium-review.googlesource.com/572079Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486805}

testing/buildbot/chromium.chromiumos.json

@@ -267,18 +267,6 @@
         },
         "test": "latency_unittests"
       },
-      {
-        "args": [
-          "--ozone-platform=headless",
-          "--override-use-software-gl-for-tests",
-          "--test-launcher-filter-file=../../testing/buildbot/filters/mash.browser_tests.filter"
-        ],
-        "swarming": {
-          "can_use_on_swarming_builders": true,
-          "hard_timeout": 900
-        },
-        "test": "mash_browser_tests"
-      },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
@@ -747,18 +735,6 @@
         },
         "test": "latency_unittests"
       },
-      {
-        "args": [
-          "--ozone-platform=headless",
-          "--override-use-software-gl-for-tests",
-          "--test-launcher-filter-file=../../testing/buildbot/filters/mash.browser_tests.filter"
-        ],
-        "swarming": {
-          "can_use_on_swarming_builders": true,
-          "hard_timeout": 900
-        },
-        "test": "mash_browser_tests"
-      },
       {
         "swarming": {
           "can_use_on_swarming_builders": true