composer.json in all packages now use 7.3.x-dev shopsys version
composer.json in all packages now use 7.3.x-dev shopsys version

- revert "all Shopsys packages are now dependent on "7.3.1" version of all other Shopsys packages instead of "7.3.x-dev""
- this reverts commit 4bd737a62372e5f0f13f6d044b1fa8fd977cad6c.

shopsys/migrations