[tests] Bump php version test (#2734)

## Summary

Hopping this fixes CICD.

## How was it tested?

CICD

## Community Contribution License

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[Apache 2 License](https://www.apache.org/licenses/LICENSE-2.0).

By creating this pull request, I represent that I have the right to
license the
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Author: mikeland73

examples/plugins/builtin/devbox.d/php82/php-fpm.conf renamed to examples/plugins/builtin/devbox.d/php84/php-fpm.conf

@@ -11,7 +11,7 @@
     }
   },
   "include": [
-    // Installs the php plugin using php82 as trigger package
-    "plugin:php82"
+    // Installs the php plugin using php84 as trigger package
+    "plugin:php84"
   ]
 }

examples/plugins/builtin/devbox.d/php82/php.ini renamed to examples/plugins/builtin/devbox.d/php84/php.ini

@@ -1,4 +1,9 @@
 {
   "lockfile_version": "1",
-  "packages": {}
+  "packages": {
+    "github:NixOS/nixpkgs/nixpkgs-unstable": {
+      "last_modified": "2025-10-23T16:27:14Z",
+      "resolved": "github:NixOS/nixpkgs/d5faa84122bc0a1fd5d378492efce4e289f8eac1?lastModified=1761236834&narHash=sha256-%2Bpthv6hrL5VLW2UqPdISGuLiUZ6SnAXdd2DdUE%2BfV2Q%3D"
+    }
+  }
 }