[ReaderMode] Replace ligature with numeric

To avoid the settings icon from being highlighted when a user enters
the "text" into the Find In Page, the icon ligature "text_format" has
been replaced with the relevant numeric code point.

Bug: 1027612
Change-Id: Ic39f9dd05b7ee23cc4af568d40bf81feeb79e192
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2133533Reviewed-by: Katie Dektar <katie@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Meredith Lane <meredithl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756562}

components/dom_distiller/core/html/dom_distiller_viewer.html

@@ -21,7 +21,7 @@ found in the LICENSE file.
       <div id="settings-container" class="desktop-only">
         <button id="settings-toggle" type="button"
             aria-label="Customize appearance" tabindex=0>
-          <i class="material-icons">text_format</i>
+          <i class="material-icons">&#xE165</i>
         </button>
         <dialog id="settings-dialog">
           <div id="settings-header">