ci: move "test difftest" to test job

Author: Firestar99

.github/workflows/ci.yaml

@@ -56,8 +56,8 @@ jobs:
       - name: rustc_codegen_spirv test
         run: cargo test -p rustc_codegen_spirv --release --no-default-features --features "use-installed-tools"
 
-      - name: workspace test (excluding examples & difftest)
-        run: cargo test --release --workspace --exclude "example-runner-*" --exclude "difftest*" --no-default-features --features "use-installed-tools,clap"
+      - name: workspace test (excluding examples)
+        run: cargo test --release --workspace --exclude "example-runner-*" --no-default-features --features "use-installed-tools,clap"
 
       # Examples
       - name: cargo check examples
@@ -198,8 +198,6 @@ jobs:
         run: cargo fetch --locked --target $TARGET
       - name: cargo fetch --locked difftests
         run: cargo fetch --locked --manifest-path=tests/difftests/tests/Cargo.toml --target $TARGET
-      - name: test difftest
-        run: cargo test -p "difftest*" --release --no-default-features --features "use-installed-tools"
       - name: difftests
         run: cargo run -p difftests --release --no-default-features --features "use-installed-tools"