Update tomasvotruba/unused-public requirement from 0.3.8 to 0.3.9 (#158)

Author: dependabot[bot]

composer.json

@@ -24,7 +24,7 @@
         "thecodingmachine/phpstan-safe-rule": "^1.2",
         "tomasvotruba/cognitive-complexity": "0.2.3",
         "tomasvotruba/type-coverage": "0.2.5",
-        "tomasvotruba/unused-public": "0.3.8"
+        "tomasvotruba/unused-public": "0.3.9"
     },
     "config": {
         "optimize-autoloader": true,