ci: don't test example-runner-*, they have no tests, just check them

Author: Firestar99

.github/workflows/ci.yaml

@@ -55,8 +55,8 @@ jobs:
       - name: rustc_codegen_spirv test
         run: cargo test -p rustc_codegen_spirv --release --no-default-features --features "use-installed-tools"
 
-      - name: workspace test
-        run: cargo test --release
+      - name: workspace test (excluding examples)
+        run: cargo test --release --workspace --exclude "example-runner-*"
 
       # Examples
       - name: cargo check examples