Fix order return checkbox selector

[SharakPL]

Questions	Answers
Description?	a9c26ce added .js- selectors in few places. The one for order returns got messed up. It's supposed to be: #order-return-form table thead input[type=checkbox], .js-order-return-form table thead input[type=checkbox] #order-return-form table tbody input[type=checkbox], .js-order-return-form table tbody input[type=checkbox] but instead it became: #order-return-form, .js-order-return-form table thead input[type=checkbox] #order-return-form, .js-order-return-form table tbody input[type=checkbox]. This pr simplifies the selectors and the function to check all products for return.
Type?	bug fix
BC breaks?	no
Deprecations?	no
Fixed ticket?	-
Sponsor company	-
How to test?	1. Have an order with several products in your customer account 2. Start a return process and see if you can check all products at once from the table header