Turn off native autocomplete for RefSelector

This commit updates the RefSelector component to not show native
autocomplete in its search box.

app/assets/javascripts/ref/components/ref_selector.vue

@@ -208,6 +208,7 @@ export default {
         ref="searchBox"
         v-model.trim="query"
         :placeholder="i18n.searchPlaceholder"
+        autocomplete="off"
         @input="onSearchBoxInput"
         @keydown.enter.prevent="onSearchBoxEnter"
       />

changelogs/unreleased/nfriend-turn-off-ref-selector-autocomplete.yml

+---
+title: Turn off native autocomplete for ref selector components
+merge_request: 56128
+author:
+type: fixed