[not verified] Fix the overlay when the block is left or right aligned (

#14820)

In WordPress/gutenberg#19593 a wrapper `div` was removed, which had a
`position` value of `relative`. Our overlay `div` to prevent the iframe
from being interacted with, relies on a parent element being
`positino: relative`. This is still the case when the block is in the
main flow/centre aligned, but when the block is left or right aligned,
it can't be selected, and clicks are handled by the iframe.

extensions/blocks/calendly/editor.scss

@@ -3,6 +3,8 @@
  */
 
 .wp-block-jetpack-calendly {
+	position: relative;
+
 	&-overlay {
 		position: absolute;
 		width: 100%;