Bump slevomat/coding-standard from 4.8.3 to 7.0.4

Bumps [slevomat/coding-standard](https://github.com/slevomat/coding-standard) from 4.8.3 to 7.0.4.
- [Release notes](https://github.com/slevomat/coding-standard/releases)
- [Commits](slevomat/coding-standard@4.8.3...7.0.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

composer.json

@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^7.3",
-        "slevomat/coding-standard": "^4.8",
+        "slevomat/coding-standard": "^7.0",
         "squizlabs/php_codesniffer": "^3.3.1"
     },
     "autoload": {