ci: use the actions from the specification's main branch

Author: ariesclark

.github/workflows/ci.yaml

@@ -36,7 +36,7 @@ jobs:
           repository: vrchatapi/vrchatapi-javascript
           ref: ${{ inputs.ref || github.ref }}
 
-      - uses: vrchatapi/specification/.github/actions/download@ci/modernise-actions
+      - uses: vrchatapi/specification/.github/actions/download@main
         with:
           url: ${{ inputs.url }}