Update mockserver to v6 (#128)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

gradle/libs.versions.toml

@@ -2,7 +2,7 @@
 annotations = "26.1.0"
 jupiter = "5.14.4"
 junit-platform = "1.14.4"
-mockserver = "5.15.0"
+mockserver = "6.1.0"
 logback = "1.5.34"
 gson = "2.14.0"