Update squizlabs/php_codesniffer requirement from ^3.6 to ^3.7

Updates the requirements on [squizlabs/php_codesniffer](https://github.com/squizlabs/PHP_CodeSniffer) to permit the latest version.
- [Release notes](https://github.com/squizlabs/PHP_CodeSniffer/releases)
- [Commits](squizlabs/PHP_CodeSniffer@3.6.0...3.7.1)

---
updated-dependencies:
- dependency-name: squizlabs/php_codesniffer
  dependency-type: direct:development
...

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

composer.json

@@ -68,7 +68,7 @@
         "phpunit/phpunit": "^9.5",
         "slim/http": "^1.2",
         "slim/psr7": "^1.5",
-        "squizlabs/php_codesniffer": "^3.6"
+        "squizlabs/php_codesniffer": "^3.7"
     },
     "autoload": {
         "psr-4": {