fix closing tag

Author: silverwind

templates/repo/issue/view_content/pull.tmpl

@@ -146,7 +146,7 @@
 					</div>
 					{{if .IsPullBranchDeletable}}
 						<div class="item-section-right">
-							<button class="delete-button ui button" data-url="{{.DeleteBranchLink}}">{{$.locale.Tr "repo.branch.delete_html"}}</a>
+							<button class="delete-button ui button" data-url="{{.DeleteBranchLink}}">{{$.locale.Tr "repo.branch.delete_html"}}</button>
 						</div>
 					{{end}}
 				</div>