Fix figcaption conditional

Author: SantosGuillamot

src/wp-includes/class-wp-block.php

@@ -357,7 +357,7 @@ public function set_content_between_figcaption_balanced_tags( $new_content ) {
 							 */
 							if (
 								WP_HTML_Processor::STATE_MATCHED_TAG !== $this->parser_state ||
-								'figcaption' !== $this->get_tag() ||
+								'FIGCAPTION' !== $this->get_tag() ||
 								$this->is_tag_closer()
 							) {
 								return false;