Diagnostics: Remove unused property on connectivity-card

- Removes 'run-button-text' from routine-section as button is always
  hidden.

Bug: 1197335
Change-Id: I2a0aa283bfe36ac5bf0d28717abbc058d7bf43fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3062680
Commit-Queue: Ashley Prasad <ashleydp@google.com>
Reviewed-by: Joon Ahn <joonbug@chromium.org>
Cr-Commit-Position: refs/heads/master@{#907333}

ash/webui/diagnostics_ui/resources/connectivity_card.html

@@ -16,7 +16,6 @@
   <network-info network="[[network]]" slot="body"></network-info>
   <routine-section slot="left-panel" routines="[[routines_]]"
       is-test-running="{{isTestRunning}}"
-      run-tests-button-text="Run Network test"
       routine-runtime="{{getEstimateRuntimeInMinutes_(routines_)}}"
       is-active="[[isActive]]"
       run-tests-automatically="true"