ci bench: remove melange pins (#7918)

Signed-off-by: Javier Chávarri <[email protected]>

Author: jchavarri

.github/workflows/bench.yml

@@ -84,17 +84,14 @@ jobs:
 
       - name: Checkout dune-melange branch
         working-directory: pupilfirst
-        run: git checkout dune-melange
+        run: git checkout b6fe6fa27814336b9e92f965449f3e010e148c4b
 
       - name: Install all deps
         working-directory: pupilfirst
         run: |
           yarn install
-          opam install -y reason
+          opam install -y reason melange reactjs-jsx-ppx rescript-syntax
           opam pin add -y graphql_ppx https://github.com/jchavarri/graphql-ppx.git\#2598910886f1d2d3869406ae7eb787341d8dce6b
-          opam pin add -y melange.dev https://github.com/melange-re/melange.git\#ebc038332c16e331ee4ab9017426e63461157cdd
-          opam pin add -y reactjs-jsx-ppx.dev https://github.com/melange-re/melange.git\#ebc038332c16e331ee4ab9017426e63461157cdd
-          opam pin add -y rescript-syntax.dev https://github.com/melange-re/melange.git\#ebc038332c16e331ee4ab9017426e63461157cdd
 
       - name: Run pupilfirst benchmark
         working-directory: pupilfirst