ci: Only run clippy on stable with fatal errors

Author: sdroege

.github/workflows/CI.yml

@@ -73,8 +73,12 @@ jobs:
         if: matrix.rust == 'beta' || matrix.rust == 'stable'
       - working-directory: ${{ matrix.conf.name }}
         name: clippy ${{ matrix.conf.name }}
-        run: cargo clippy --all-targets -- -D warnings -A unknown-lints
-        if: matrix.rust == 'beta' || matrix.rust == 'stable'
+        run: cargo clippy --all-targets -- -D warnings
+        if: matrix.rust == 'stable'
+      - working-directory: ${{ matrix.conf.name }}
+        name: clippy ${{ matrix.conf.name }}
+        run: cargo clippy --all-targets
+        if: matrix.rust == 'beta'
       # tests
       - name: tests (rust ${{ matrix.rust }})
         run: xvfb-run --auto-servernum cargo test --manifest-path ${{ matrix.conf.name }}/Cargo.toml --features "${{ matrix.conf.features }}"