Make dartfunctions experiment public

This boolean flip will make it visible to CLI users when running
`firebase experiments:list`.

Author: wandamora

src/experiments.ts

@@ -88,7 +88,7 @@ export const ALL_EXPERIMENTS = experiments({
   },
   dartfunctions: {
     shortDescription: "Enable Dart Functions.",
-    public: false,
+    public: true,
     default: false,
   },