Make Reset Settings section not be hidden by default.

The Reset Settings section in Advanced Settings used to be hidden by
default, and then enabled if the profile was OffTheRecord. CL
https://codereview.chromium.org/467363003 changed this setting to be
hidden if guest mode is set, but did not ever remove the hidden flag.
Thus, it was only ever hidden.

In this CL the Reset Settings section is now visible by default. It
still gets hidden by guest mode.

BUG=407493

Review URL: https://codereview.chromium.org/505143002

Cr-Commit-Position: refs/heads/master@{#291948}

chrome/browser/resources/options/browser_options.html

@@ -961,7 +961,7 @@
     </div>
   </section>
 </if>
-  <section id="reset-profile-settings-section" hidden>
+  <section id="reset-profile-settings-section">
     <h3 i18n-content="resetProfileSettingsSectionTitle"></h3>
     <div>
       <span class="settings-row" i18n-content="resetProfileSettingsDescription">