fix: remove redundant is_string check in sensitive field sanitization

Author: ajaydsouza

includes/admin/settings/class-settings-sanitize.php

@@ -283,7 +283,7 @@ public function sanitize_sensitive_field( $value, $key ) {
 		}
 
 		// If input is masked, return existing encrypted key.
-		if ( is_string( $value ) && strpos( $value, '**' ) !== false ) {
+		if ( strpos( $value, '**' ) !== false ) {
 			return $stored_encrypted_key;
 		}