minor #12338 [DOCS] Updating the controller customization (Roshyo)
minor #12338 [DOCS] Updating the controller customization (Roshyo)

This PR was merged into the 1.9 branch.

Discussion
----------

| Q               | A
| --------------- | -----
| Branch?         | 1.9
| Bug fix?        | no
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no (but fixing one :D )
| Related tickets | N/A
| License         | MIT

* Fix the last route declaration to its real use
* Use the term `make sure` instead of `check if` since it is should to work
* use the double `:` syntax for controllers instead of the deprecated single `:`


Commits
-------

f1028ab0d4c73606373d4372502af1d680e004e5 Updating the controller customization doc
4f6b2de629da9927735b7789a1858adc266b6e65 Update docs/customization/controller.rst

Arminek/Sylius,Sylius/Sylius,Sylius/Sylius,pamil/Sylius,pamil/Sylius,Zales0123/Sylius,GSadee/Sylius,SyliusBot/Sylius,diimpp/Sylius,lchrusciel/Sylius,antonioperic/Sylius,101medialab/Sylius,GSadee/Sylius,Zales0123/Sylius,diimpp/Sylius,Sylius/Sylius,loic425/Sylius,Zales0123/Sylius,pamil/Sylius,GSadee/Sylius,SyliusBot/Sylius,Arminek/Sylius,loic425/Sylius,diimpp/Sylius,antonioperic/Sylius,101medialab/Sylius,lchrusciel/Sylius,lchrusciel/Sylius,antonioperic/Sylius,loic425/Sylius,Arminek/Sylius,101medialab/Sylius,SyliusBot/Sylius