Try re-enabling semver checks

Author: tarcieri

.github/workflows/ci.yml

@@ -134,7 +134,6 @@ jobs:
       - run: cargo +nightly careful setup && cargo +nightly careful test --features=tests-exhaustive
 
   semver:
-    if: false # TODO(tarcieri): re-enable after breaking `crypto-bigint` changes are complete
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4