minor Sylius#10121 [GridBundle] Doc improvement (Roshyo)

This PR was merged into the 1.5-dev branch.

Discussion
----------

This is mentioned in 2.3 of the doc, but should be also said here.

| Q               | A
| --------------- | -----
| Branch?         | 1.2
| Bug fix?        | no
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | 
| License         | MIT


Commits
-------

61f06d4 Update configuration.rst
1c4f743 Update configuration.rst

docs/components_and_bundles/bundles/SyliusGridBundle/configuration.rst

@@ -12,6 +12,10 @@ Here you will find all configuration options of ``sylius_grid``.
                     name: doctrine/orm
                     options:
                         class: "%app.model.user%"
+                        repository:
+                            method: myCustomMethod
+                            arguments:
+                                id: resource.id
                 sorting:
                     name: asc
                 limits: [10, 25, 50, 100]