chore: Update Shopware 6.5.8 tag to v6.5.8.15 (#37)

Author: schneider-felix

.github/workflows/build-docker-images.yaml

@@ -231,7 +231,7 @@ jobs:
             php-version: "8.1"
             flavour: alpine
             template: https://github.com/shopware/shopware
-          - shopware-version: v6.5.8.13
+          - shopware-version: v6.5.8.15
             php-version: "8.1"
             flavour: alpine
             template: https://github.com/shopware/shopware
@@ -399,7 +399,7 @@ jobs:
             php-version: "8.1"
             flavour: debian
             template: https://github.com/shopware/shopware
-          - shopware-version: v6.5.8.13
+          - shopware-version: v6.5.8.15
             php-version: "8.1"
             flavour: debian
             template: https://github.com/shopware/shopware