Pin codpeed action (#5064)

Pin codspeed action to 4.2.1 while it seems like there's some issue with
the new release.

- CodSpeedHQ/action#149

Signed-off-by: Adam Gutglick <[email protected]>

Author: AdamGS

.github/workflows/ci.yml

@@ -523,7 +523,7 @@ jobs:
             --profile bench
 
       - name: Run benchmarks
-        uses: CodSpeedHQ/action@v4
+        uses: CodSpeedHQ/action@c6574d0c2a990bca2842ce9af71549c5bfd7fbe0
         with:
           run: cargo codspeed run
           token: ${{ secrets.CODSPEED_TOKEN }}