Update dependency org.mockito:mockito-core to v5.12.0

Author: renovate[bot]

javalin-demo/gradle.properties

@@ -14,7 +14,7 @@ commonsEmail=1.6.0
 # Testing
 junitVersion=5.10.2
 assertjVersion=3.25.3
-mockitoVersion=5.11.0
+mockitoVersion=5.12.0
 seleniumChromeVersion=4.18.1
 seleniumHttpJdkVersion=4.13.0
 webdrivermanagerVersion=5.8.0