fix(deps): update dependency org.jfree:jfreechart to v1.5.6 (#354)

Author: renovate-bot

build.gradle.kts

@@ -34,7 +34,7 @@ dependencies {
 
     implementation("com.itextpdf:itextpdf:5.5.13.4")
     implementation("com.jcraft:jsch:0.1.55")
-    implementation("org.jfree:jfreechart:1.5.5")
+    implementation("org.jfree:jfreechart:1.5.6")
 
     testImplementation("org.junit.jupiter:junit-jupiter:5.12.2")
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")