Pontoon/AMO Frontend: Update English (Great Britain) (en-GB)

Co-authored-by: Ian Neal <[email protected]> (en-GB)

Author: mozilla-pontoon

locale/en_GB/LC_MESSAGES/amo.po

@@ -1667,11 +1667,11 @@ msgstr "Permissions"
 
 #: src/amo/components/PermissionsCard/index.js:84
 msgid "Required permissions:"
-msgstr ""
+msgstr "Required permissions:"
 
 #: src/amo/components/PermissionsCard/index.js:94
 msgid "Optional permissions:"
-msgstr ""
+msgstr "Optional permissions:"
 
 #: src/amo/components/PermissionsCard/permissions.js:27
 msgid "Read and modify bookmarks"