fix CI

Author: hhugo

.github/workflows/build-wasm_of_ocaml.yml

@@ -136,6 +136,10 @@ jobs:
         working-directory: ./wasm_of_ocaml
         run: opam exec -- dune build @runtest-wasm --profile with-effects
 
+      - name: pin sedlex
+        if: matrix.all_jane_street_tests
+        run: opam pin add sedlex 3.4
+
       - name: Run Base tests
         if: matrix.all_jane_street_tests
         continue-on-error: ${{ matrix.os == 'windows-latest' }}