ci: Downgrade libloading in msrv test

Author: ids1024

.github/workflows/ci.yml

@@ -212,6 +212,12 @@ jobs:
       - name: System dependencies
         run: sudo apt-get install libwayland-dev
 
+      - name: Downgrade libloading
+        uses: actions-rs/cargo@v1
+        with:
+          command: update
+          args: -p libloading --precise 0.8.8
+
       - name: Check
         uses: actions-rs/cargo@v1
         with: