chore: upgrade to CodSpeedHQ/action@v4

Use the `intrumentation` mode to get reliable results

Author: samueltardieu

.github/workflows/codspeed.yml

@@ -38,7 +38,8 @@ jobs:
           command: codspeed
           args: build
 
-      - uses: CodSpeedHQ/action@v3
+      - uses: CodSpeedHQ/action@v4
         name: Run benchmarks
         with:
           run: cargo codspeed run
+          mode: instrumentation