Add a needle for cut-off Firefox 'close tabs' button

This dialog gets cut off sometimes, it seems. That's a bug, but
we just want to handle it, because we want to quit cleanly.

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

needles/firefox/firefox_close_tabs-cutoff-20210330.json

@@ -0,0 +1,16 @@
+{
+  "area": [
+    {
+      "height": 11,
+      "xpos": 650,
+      "ypos": 464,
+      "type": "match",
+      "width": 75
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "apps_run_firefox_stop",
+    "firefox_close_tabs"
+  ]
+}