Update phpmd/phpmd requirement from ~2.6.0 to ~2.10.0

Updates the requirements on [phpmd/phpmd](https://github.com/phpmd/phpmd) to permit the latest version.
- [Release notes](https://github.com/phpmd/phpmd/releases)
- [Changelog](https://github.com/phpmd/phpmd/blob/master/CHANGELOG)
- [Commits](phpmd/phpmd@2.6.0...2.10.0)

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

composer.json

@@ -24,7 +24,7 @@
   "require-dev": {
     "phpunit/phpunit": "^7.5",
     "squizlabs/php_codesniffer": "^3.4",
-    "phpmd/phpmd": "~2.6.0",
+    "phpmd/phpmd": "~2.10.0",
     "magento/magento-coding-standard": "*"
   },
   "repositories": {