Revert "extensions: change to singular term in context menu"

This reverts commit c71f4c7c.

Reason for revert: Missing screenshots crbug.com/1113762

Original change's description:
> extensions: change to singular term in context menu
> 
> when clicking the "Manage extensions" button in the context menu,
> we go to the chrome://extensions page for that extension instead
> of all the extensions.
> 
> Bug: 986890
> Change-Id: I1e17b4ad0ffebc5c38591cc3fae2953efd8aa0fe
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2233303
> Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
> Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#795279}

TBR=rdevlin.cronin@chromium.org,andreas@apap04.com

Change-Id: I0b23e078b3ab543c78c867c118058d955f13ef2f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 986890
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2340669Reviewed-by: Ben Mason <benmason@chromium.org>
Commit-Queue: Ben Mason <benmason@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795493}

chrome/app/generated_resources.grd

@@ -4375,10 +4375,7 @@ are declared in tools/grit/grit_rule.gni.
           <message name="IDS_EXTENSIONS_UNPIN_FROM_TOOLBAR" desc="The text for the menu item to unpin an extension from the toolbar (sentence case).">
             Unpin
           </message>
-          <message name="IDS_MANAGE_EXTENSION" desc="The text of the button in the extensions toolbar menu used to open the chrome://extensions/?id=xxx page and manage a specific extension (sentence case).">
-            Manage extension
-          </message>
-          <message name="IDS_MANAGE_EXTENSIONS" desc="The text of the button in the extensions toolbar menu used to open the chrome://extensions page and manage all extensions (sentence case).">
+          <message name="IDS_MANAGE_EXTENSION" desc="The 'Manage extensions' text in the context menu for when right-clicking on extension icons (sentence case).">
             Manage extensions
           </message>
           <message name="IDS_EXTENSION_ACTION_INSPECT_POPUP" desc="The text for the right-click menu of page and browser actions which shows the popup and opens the developer tools (sentence case).">
@@ -4428,10 +4425,7 @@ are declared in tools/grit/grit_rule.gni.
           <message name="IDS_EXTENSIONS_UNPIN_FROM_TOOLBAR" desc="The text for the menu item to unpin an extension from the toolbar (title case).">
             Unpin
           </message>
-          <message name="IDS_MANAGE_EXTENSION" desc="The text of the button in the extensions toolbar menu used to open the chrome://extensions/?id=xxx page and manage a specific extension (title case).">
-            Manage Extension
-          </message>
-          <message name="IDS_MANAGE_EXTENSIONS" desc="The text of the button in the extensions toolbar menu used to open the chrome://extensions page and manage all extensions (title case).">
+          <message name="IDS_MANAGE_EXTENSION" desc="The 'Manage Extensions' text in the context menu for when right-clicking on extension icons (title case).">
             Manage Extensions
           </message>
           <message name="IDS_EXTENSION_ACTION_INSPECT_POPUP" desc="The text for the right-click menu of page and browser actions which shows the popup and opens the developer tools (title case).">

chrome/app/generated_resources_grd/IDS_MANAGE_EXTENSION.png.sha1

-ddad08f0e2929c3a315cd1dc020111603bbc2f96
\ No newline at end of file

chrome/app/generated_resources_grd/IDS_MANAGE_EXTENSIONS.png.sha1

-6a0b078c96d8677bb469218cbd98eb693a82c86d
\ No newline at end of file

chrome/browser/ui/views/extensions/extensions_menu_view.cc

@@ -149,7 +149,7 @@ void ExtensionsMenuView::Populate() {
   AddChildView(std::make_unique<views::Separator>());
 
   auto footer = CreateBubbleMenuItem(
-      EXTENSIONS_SETTINGS_ID, l10n_util::GetStringUTF16(IDS_MANAGE_EXTENSIONS),
+      EXTENSIONS_SETTINGS_ID, l10n_util::GetStringUTF16(IDS_MANAGE_EXTENSION),
       &button_listener_);
   footer->SetImage(
       views::Button::STATE_NORMAL,