Change title text for Associated Site Template panel.

See cuny-academic-commons/commons-in-a-box#571.

Author: boonebgorges

views/site-template/template-picker.php

@@ -1,5 +1,5 @@
 <div class="panel panel-default panel-template-picker hidden">
-	<div class="panel-heading"><?php esc_html_e( 'Associated Site Template', 'cboxol-site-template-picker' ); ?></div>
+	<div class="panel-heading"><?php esc_html_e( 'Choose an Associated Site Template (Required)', 'cboxol-site-template-picker' ); ?></div>
 	<div class="panel-body">
 		<?php if ( $gloss ) : ?>
 			<p class="site-template-gloss"><?php echo wp_kses_post( $gloss ); ?></p>