composer.json: use "proprietary" instead of "Shopsys Community Licens…

…e" as a version identifier

- Packagist requires the package license to be either a valid SPDX identifier (https://spdx.org/licenses/) or "proprietary"

composer.json

@@ -2,7 +2,7 @@
     "name": "shopsys/framework",
     "type": "library",
     "description": "Core of Shopsys Framework - open source framework for building large, scalable, fast-growing e-commerce projects based on Symfony",
-    "license": "Shopsys Community License",
+    "license": "proprietary",
     "autoload": {
         "psr-4": {
             "Shopsys\\FrameworkBundle\\": [