ci: Pin clippy to rust 1.78.0

Author: ValuedMammal

.github/workflows/cont_integration.yml

@@ -118,7 +118,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions-rs/toolchain@v1
         with:
-            toolchain: stable
+            toolchain: 1.78.0
             components: clippy
             override: true
       - name: Rust Cache