Update experience blocks for WP 5.9 compat

[roborourke]

There have been some changes to InnerBlocks in WP 5.9:

https://make.wordpress.org/core/2021/12/28/take-more-control-over-inner-block-areas-as-a-block-developer/

Acceptance criteria:

• [ ] Update to using hooks useInnerBlocksProps()
• [ ] Ensure there are no JS or PHP deprecation notices coming from this plugin's code

[roborourke]

Hey team! Please add your planning poker estimate with ZenHub @mikelittle @robindevitt @shadyvb

[veselala]

@roborourke we've estimated this on 5 and moved it to the backlog