Update merge request widget question mark icons

Use the filled question icon per https://design.gitlab.com/usability/helping-users/#formatting-help-content

app/assets/javascripts/vue_merge_request_widget/components/states/squash_before_merge.vue

@@ -51,7 +51,7 @@ export default {
       rel="noopener noreferrer nofollow"
       data-container="body"
     >
-      <icon name="question-o" />
+      <icon name="question" />
     </a>
   </div>
 </template>

ee/app/assets/javascripts/approvals/components/empty_rule_name.vue

@@ -25,7 +25,7 @@ export default {
       <icon
         id="pop-approver"
         tabindex="0"
-        name="question-o"
+        name="question"
         :aria-label="__('help')"
         :size="14"
         class="author-link suggestion-help-hover"

ee/app/assets/javascripts/vue_merge_request_widget/components/approvals/approvals_summary_optional.vue

@@ -41,7 +41,7 @@ export default {
       target="_blank"
       class="d-flex-center pl-1"
     >
-      <icon name="question-o" />
+      <icon name="question" />
     </gl-link>
   </div>
 </template>