Run fetching core libs on ubuntu

Author: tomwyr

.github/workflows/run-tests.yaml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   fetch-core-libs:
-    runs-on: macos-14
+    runs-on: ubuntu-22.04
     env:
       CORE_LIB_REPO: tomwyr/godot-node-tree-core
     steps: