Revert "Feature: Add monitor-switch buttons to remote toolbars (#15314)" (#15338)

This reverts commit 7c8b0adc1e.

flutter/assets/display_switcher.svg

@@ -1,7 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" viewBox="0 0 32 32">
-  <g fill="#000000" fill-rule="evenodd">
-    <rect x="4" y="6" width="24" height="16" rx="3"/>
-    <rect x="14.5" y="22" width="3" height="2"/>
-    <rect x="9.5" y="24" width="13" height="2.5" rx="1.25"/>
-  </g>
-</svg>