Disable Firefox E2E tests (#21363)

Make CI green again, until we figure out
https://github.com/go-gitea/gitea/issues/21355.

playwright.config.js

@@ -64,12 +64,13 @@ export default {
       },
     },
 
-    {
+    // disabled because of https://github.com/go-gitea/gitea/issues/21355
-      name: 'firefox',
+    // {
-      use: {
+    //   name: 'firefox',
-        ...devices['Desktop Firefox'],
+    //   use: {
-      },
+    //     ...devices['Desktop Firefox'],
-    },
+    //   },
+    // },
 
     {
       name: 'webkit',