bug #13019 [Bug] Fix default sylius config file path in Sylius 1.9 (l…

…chrusciel)

This PR was merged into the 1.9 branch.

Discussion
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| Q               | A
| --------------- | -----
| Branch?         | 1.9
| Bug fix?        | yes
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | 
| License         | MIT

There is no such file as `app/config/packages/_sylius.yaml`. App prefix is not needed, because related configuration should be placed in: https://github.com/Sylius/Sylius-Standard/blob/1.10/config/packages/_sylius.yaml

This PR contains fixes to 1.8 as well, as I'm not sure if we want to merge then on previous branch

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Commits
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068cc65 [Bug] Fix default sylius config file path in Sylius 1.9

UPGRADE-1.9.md

@@ -1,6 +1,6 @@
 # UPGRADE FROM `v1.9.5` TO `v1.9.6`
 
-1. API is disabled by default, to enable it you need to set flag to ``true`` in ``app/config/packages/_sylius.yaml``:
+1. API is disabled by default, to enable it you need to set flag to ``true`` in ``config/packages/_sylius.yaml``:
 
     ```yaml
     sylius_api:

UPGRADE-API-1.9.md

@@ -1,6 +1,6 @@
 # UPGRADE FROM `v1.9.5` TO `v1.9.6`
 
-1. API is disabled by default, to enable it you need to set flag to ``true`` in ``app/config/packages/_sylius.yaml``:
+1. API is disabled by default, to enable it you need to set flag to ``true`` in ``config/packages/_sylius.yaml``:
 
     ```yaml
     sylius_api: