FE Docs: Fix header hierarchy in Vuex section of Vue.md

doc/development/fe_guide/vue.md

@@ -523,7 +523,7 @@ export default new Vuex.Store({
 ```
 _Note:_ If the state of the application is too complex, an individual file for the state may be better.
 
-#### `actions.js`
+##### `actions.js`
 An action commits a mutatation. In this file, we will write the actions that will call the respective mutation:
 
 ```javascript
@@ -550,7 +550,7 @@ import { mapActions } from 'vuex';
 };
 ```
 
-#### `getters.js`
+##### `getters.js`
 Sometimes we may need to get derived state based on store state, like filtering for a specific prop. This can be done through the `getters`:
 
 ```javascript
@@ -573,7 +573,7 @@ import { mapGetters } from 'vuex';
 };
 ```
 
-#### `mutations.js`
+##### `mutations.js`
 The only way to actually change state in a Vuex store is by committing a mutation.
 
 ```javascript
@@ -586,7 +586,7 @@ The only way to actually change state in a Vuex store is by committing a mutatio
   };
 ```
 
-#### `mutations_types.js`
+##### `mutations_types.js`
 From [vuex mutations docs][vuex-mutations]:
 > It is a commonly seen pattern to use constants for mutation types in various Flux implementations. This allows the code to take advantage of tooling like linters, and putting all constants in a single file allows your collaborators to get an at-a-glance view of what mutations are possible in the entire application.