Delete an unused message

Bug: T364205
Change-Id: Id09f5d0537861230084783fb5958401b35aae38a

i18n/en.json

@@ -25,7 +25,6 @@
 	"mobile-frontend-meta-data-issues-categories": "About this category",
 	"mobile-frontend-meta-data-issues-header": "Page issues",
 	"minerva-meta-data-issues-section-header": "Section issues",
-	"mobile-frontend-notifications-filter": "Filter",
 	"mobile-frontend-pageaction-edit-tooltip": "Edit the lead section of this page",
 	"mobile-frontend-placeholder": "Search {{SITENAME}}",
 	"mobile-frontend-random-button": "Random",

i18n/qqq.json

@@ -39,7 +39,6 @@
 	"mobile-frontend-meta-data-issues-categories": "Label to appear in button that opens issue overlay on categories.",
 	"mobile-frontend-meta-data-issues-header": "Heading for overlay listing all cleanup templates\n{{Identical|Issue}}",
 	"minerva-meta-data-issues-section-header": "Heading for overlay listing all cleanup templates in a section \n{{Identical|Issue}}",
-	"mobile-frontend-notifications-filter": "Caption of the button on the notifications page that opens the filter panel",
 	"mobile-frontend-pageaction-edit-tooltip": "Tooltip that appears when you hover over the edit icon at the top of the page in the page action bar.",
 	"mobile-frontend-placeholder": "Phrase used to prompt user to use search interface for mobile full screen search\n{{Identical|Search}}",
 	"mobile-frontend-random-button": "This appears in the mobile web menu, which appears when tapping the three stripes at the top corner.\n\nThis button takes the user to a random page.\n{{Identical|Random}}",

skin.json

@@ -510,7 +510,6 @@
 				"skin-minerva-time-ago-months",
 				"skin-minerva-time-ago-years",
 				"echo-badge-count",
-				"mobile-frontend-notifications-filter",
 				"skin-minerva-issue-learn-more",
 				"mobile-frontend-meta-data-issues",
 				"minerva-meta-data-issues-section-header",