Fixes a label in Clear Browsing Data dialog.

Fixes brave/brave-browser#6627

The label used to be set based on a flag that's no longer available
causing our label in OnExit tab to differ from the Advanced tab.

Chromium change:

https://chromium.googlesource.com/chromium/src/+/a3f57021dd6ac0f0df8e473da36f874d4132819f

commit a3f57021dd6ac0f0df8e473da36f874d4132819f
Author: Maggie Cai <mxcai@chromium.org>
Date:   Wed Jul 17 01:03:22 2019 +0000

    Settings: Remove site-settings flag.

    All sites is launched in M74, this CL removes site-settings flag.

    BUG=980426

browser/resources/settings/brave_clear_browsing_data_dialog/brave_clear_browsing_data_on_exit_page.html

@@ -60,9 +60,7 @@
  </settings-checkbox>
  <settings-checkbox id="siteSettingsCheckboxOnExit"
  pref="{{prefs.browser.clear_data.site_settings_on_exit}}"
- label="[[siteSettingsLabel_(
- '$i18nPolymer{siteSettings}',
- '$i18nPolymer{contentSettings}')]]"
+ label="$i18nPolymer{siteSettings}"
  sub-label="[[counters.site_settings]]"
  no-set-pref>
  </settings-checkbox>

browser/resources/settings/brave_clear_browsing_data_dialog/brave_clear_browsing_data_on_exit_page.js

@@ -54,11 +54,6 @@ Polymer({
  return changed;
  },
 
- siteSettingsLabel_: function (siteSettings, contentSettings) {
- return loadTimeData.getBoolean('enableSiteSettings') ? siteSettings :
- contentSettings;
- },
-
  updateModified_: function (checkbox) {
  let modified = false;
  const boxes = this.$.checkboxes.querySelectorAll('settings-checkbox');