Allow authenticated users to query signUpEnabled

The signUpEnabled field used @session(required: NONE) which rejects
authenticated users. Change it to OPTIONAL so the query works regardless
of authentication state, fixing a crash on the sign-up page for
already-logged-in users.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/server/api/connect/v1/schema.graphql

@@ -57,7 +57,7 @@ type Query {
     @session(required: OPTIONAL)
   signUpEnabled: Boolean!
     @goField(forceResolver: true)
-    @session(required: NONE)
+    @session(required: OPTIONAL)
 }
 
 type Mutation {