bump cache key

Author: jmgrosen

dist/index.cjs

@@ -49,6 +49,7 @@ async function composeOpamCacheKeys() {
     ocamlCompiler,
     repositoryUrls,
     sandbox,
+    "v2",
   ].join();
   const hash = crypto.createHash("sha256").update(plainKey).digest("hex");
   const key = `${CACHE_PREFIX}-setup-ocaml-opam-${hash}`;