Consolidate Firefox launcher needles

apps_menu_firefox and firefox/launcher are matching on the same
thing. Also, launcher-kde actually happens to match current
GNOME, so rename it to be generic. Give the launcher needles
the apps_menu_firefox tags and wipe the apps_menu_firefox
needle.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/firefox/launcher-20210211.json

@@ -11,6 +11,7 @@
   "properties": [],
   "tags": [
     "browser_launcher",
-    "firefox_launcher"
+    "firefox_launcher",
+    "apps_menu_firefox"
   ]
-}
+}

needles/firefox/launcher-gnome-20210226.json

@@ -12,6 +12,7 @@
   "tags": [
     "DESKTOP-gnome",
     "browser_launcher",
-    "firefox_launcher"
+    "firefox_launcher",
+    "apps_menu_firefox"
   ]
-}
+}

needles/gnome/apps/apps_menu_firefox-20210304.json

@@ -1,15 +0,0 @@
-{
-  "area": [
-    {
-      "height": 19,
-      "ypos": 709,
-      "xpos": 350,
-      "width": 24,
-      "type": "match"
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "apps_menu_firefox"
-  ]
-}