Fix lock modal content rendering outside modal (#15095)

* Fix lock modal content rendering outside modal

The .content was not a child to .modal so was rendering outside. This is
a recent regression but I'm not certain when it was introduced.

* remove extraneous closing div

templates/repo/issue/view_content/sidebar.tmpl

@@ -578,8 +578,6 @@
 					{{end}}
 				</button>
 			</div>
-
-
 			<div class="ui tiny modal" id="lock">
 				<div class="header">
 					{{ if .Issue.IsLocked }}
@@ -588,7 +586,6 @@
 						{{.i18n.Tr "repo.issues.lock.title"}}
 					{{end}}
 				</div>
-			</div>
 				<div class="content">
 					<div class="ui warning message text left">
 						{{ if .Issue.IsLocked }}