Revert "[Custom Tabs] Implement "Read It Later" Behind a Flag"

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index e4e0a6152bc54e5f738cee5a9060fc241fa241c7..7f531a68ac6efad51aad0e91d9e507f6b8be6212 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -5920,12 +5920,6 @@ Keep your key file in a safe place. You will need it to create new versions of y
         Enable web pages to use experimental WebAssembly.
       </message>
       <if expr="is_android">
-        <message name="IDS_FLAGS_ENABLE_READ_IT_LATER_IN_MENU_NAME" desc="Title for the flag to use system download manager.">
-          Enable read it later in app menu.
-        </message>
-        <message name="IDS_FLAGS_ENABLE_READ_IT_LATER_IN_MENU_DESCRIPTION" desc="Description for the flag to show read it later in menu.">
-          Allow "read it later" to show in the menu, and users can select it to save the tab to Chrome in background.
-        </message>
         <message name="IDS_FLAGS_MEDIA_DOCUMENT_DOWNLOAD_BUTTON_NAME" desc="Title for the flag to enable the download button on MediaDocument.">
           Download button when opening a page with media url.
         </message>