Fixes https://github.com/payloadcms/payload/issues/9288
### What?
When a block had a subfield named `blocks`, sanitization would throw an
error.
### Why?
An incorrect check for the key of `"fields"` would then attempt to pass
`data.blocks[key].fields` aka `data.blocks.fields.fields` to the next
call of `areAllPermissionsTrue` which would be undefined. Instead if the
key is `fields` it should pass `data.blocks[key]`.
### How?
Remove the second `.fields` property accessor.
5503afdf29