minor #943 Outdated SyliusCon advert removal (Rafikooo)

This PR was merged into the 1.12 branch.

Discussion
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The conference has already taken place, so we can remove this outdated ad 🕺 

Commits
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  Remove outdated SyliusCon advert

composer.json

@@ -115,8 +115,7 @@
         "post-create-project-cmd": [
             "@php -r \"file_put_contents('.gitignore', str_replace('/composer.lock' . PHP_EOL, '', file_get_contents('.gitignore')));\"",
             "@php bin/console sylius:inform-about-gus --ansi",
-            "@php bin/console sylius:show-available-plugins --ansi",
-            "echo 'Join us at this year’s \uD83E\uDDA2 SyliusCon \uD83E\uDDA2: https://sylius.com/conference'"
+            "@php bin/console sylius:show-available-plugins --ansi"
         ],
         "auto-scripts": {
             "cache:clear": "symfony-cmd",