Reduce z-index for pledge background

- reduces the z-index from 251 to 99, to avoid the form not being editable.

themes/wporg-5ftf-2024/src/pledge-edit-button/style.scss

@@ -47,7 +47,7 @@
 
 .pledge-dialog__background {
 	position: fixed;
-	z-index: 251; /* header + 1. */
+	z-index: 99;
 	top: 0;
 	left: 0;
 	bottom: 0;