fix(actions-and-reducers.mdx): remove extra colon in code snippet

docs/zkapps/writing-a-zkapp/feature-overview/actions-and-reducer.mdx

@@ -82,7 +82,7 @@ let newState = this.reducer.reduce(
   actions,
   stateType,
   (state: Bool, action: Field) => state.or(action.equals(1000)),
-  initial: 
+  initial 
 );
 ```