Remove viz_content_browsertests from Linux Mojo FYI bot

The Linux Mojo FYI bot is intended for testing just network services, in
preparation for moving the tests to the CQ. However in the interim this can
sometimes be ran on the CQ.

viz_content_browsertests that run on the FYI bots are intented to sometimes
fail, and are not CQ ready.

Due to this I'm removing them from this config until I can find a more
appropriate FYI bot.


TEST=viz_content_browsertests

Bug: 760181
Change-Id: Ia5a5712162d24267b8ce5414d2c1e59b73106171
Reviewed-on: https://chromium-review.googlesource.com/803800Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521150}

testing/buildbot/chromium.fyi.json

@@ -4580,18 +4580,6 @@
           "can_use_on_swarming_builders": true
         },
         "test": "content_browsertests"
-      },
-      {
-        "args": [
-          "--enable-viz",
-          "--test-launcher-filter-file=../../testing/buildbot/filters/mojo.fyi.viz.content_browsertests.filter"
-        ],
-        "name": "viz_content_browsertests",
-        "swarming": {
-          "can_use_on_swarming_builders": true,
-          "shards": 2
-        },
-        "test": "content_browsertests"
       }
     ],
     "isolated_scripts": [