Set autocomplete off on branches selector

Fix #15782

Signed-off-by: Andrew Thornton <[email protected]>

Author: zeripath

templates/repo/branch_dropdown.tmpl

@@ -31,7 +31,7 @@
 		<div class="menu transition" :class="{visible: menuVisible}" v-if="menuVisible" v-cloak>
 			<div class="ui icon search input">
 				<i class="icon df ac jc m-0">{{svg "octicon-filter" 16}}</i>
-				<input name="search" ref="searchField" v-model="searchTerm" @keydown="keydown($event)" placeholder="{{if $showBranchesInDropdown}}{{.root.i18n.Tr "repo.filter_branch_and_tag"}}{{else}}{{.root.i18n.Tr "repo.find_tag"}}{{end}}...">
+				<input name="search" ref="searchField" autocomplete="off" v-model="searchTerm" @keydown="keydown($event)" placeholder="{{if $showBranchesInDropdown}}{{.root.i18n.Tr "repo.filter_branch_and_tag"}}{{else}}{{.root.i18n.Tr "repo.find_tag"}}{{end}}...">
 			</div>
 			{{if $showBranchesInDropdown}}
 				<div class="header branch-tag-choice">