Update a couple of Firefox needles for changes in 88

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

needles/firefox/download_complete-20210422.json

@@ -0,0 +1,16 @@
+{
+  "area": [
+    {
+      "height": 19,
+      "width": 16,
+      "ypos": 73,
+      "xpos": 860,
+      "type": "match"
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "browser_download_complete",
+    "firefox_download_complete"
+  ]
+}

needles/firefox/firefox_close_tabs-downcase-20210422.json

@@ -0,0 +1,16 @@
+{
+  "area": [
+    {
+      "type": "match",
+      "xpos": 599,
+      "ypos": 431,
+      "height": 13,
+      "width": 75
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "apps_run_firefox_stop",
+    "firefox_close_tabs"
+  ]
+}