Simplify unused snapshot check (#1525)

.github/workflows/ci.yaml

@@ -116,18 +116,12 @@ jobs:
             ${{ runner.os }}-build-${{ env.cache-name }}-
             ${{ runner.os }}-build-
             ${{ runner.os }}-
+      - run: cargo install cargo-insta
       - run: pip install black[d]==22.12.0
       - name: Run tests
         run: |
-          export INSTA_SNAPSHOT_REFERENCES_FILE="$(mktemp)"
-          cargo test --all
-          USED_SNAPSHOTS=$(cat $INSTA_SNAPSHOT_REFERENCES_FILE | xargs realpath --relative-to $PWD)
-          UNUSED_SNAPSHOTS=$(cat <(git ls-files '*.snap') <(echo "$USED_SNAPSHOTS") | sort | uniq -u)
-          if [ ! -z "$UNUSED_SNAPSHOTS" ]; then
-            echo "Found unused snapshots:"
-            echo "$UNUSED_SNAPSHOTS"
-            exit 1
-          fi
+          cargo insta test --all --delete-unreferenced-snapshots
+          git diff --exit-code
       - run: cargo test --package ruff --test black_compatibility_test -- --ignored
 
 # TODO(charlie): Re-enable the `wasm-pack` tests.