ci(nopin): pinning is very slow and not necessary

'opam install --deps-only --with-test .' should work without pinning.
And then 'dune build' should work as normal, we don't want to retain any of the
packages at the end of the build, so no need to pin (in theory).

Signed-off-by: Edwin Török <[email protected]>

.github/workflows/setup-xapi-environment/action.yml

@@ -48,6 +48,7 @@ runs:
         ocaml-compiler: ${{ steps.dotenv.outputs.ocaml_version_full }}
         opam-repositories: |
           xs-opam: ${{ steps.dotenv.outputs.repository }}
+        opam-pin: false
         dune-cache: true
 
     - name: Install dependencies