jfreechart 1.5.2 and remove some slf4j/log4j dependency definitions (#226)

* jfreechart 1.5.2
* remove explicit slf4j log4j dependency definitions, which are anyway contained by other log4j

Author: Pitterling

build.gradle

@@ -19,14 +19,12 @@ repositories {
 }
 
 dependencies {
-    implementation group: 'org.slf4j', name: 'slf4j-api', version: '1.7.30'
     implementation group: 'org.apache.logging.log4j', name: 'log4j-slf4j-impl', version: '2.14.0'
-    implementation group: 'org.apache.logging.log4j', name: 'log4j-api', version: '2.14.0'
     implementation group: 'org.apache.logging.log4j', name: 'log4j-core', version: '2.14.0'
 
     implementation group: 'com.itextpdf', name: 'itextpdf', version: '5.5.13.2'
     implementation group: 'com.jcraft', name: 'jsch', version: '0.1.55'
-    implementation group: 'org.jfree', name: 'jfreechart', version: '1.5.1'
+    implementation group: 'org.jfree', name: 'jfreechart', version: '1.5.2'
     testImplementation 'junit:junit:4.13.1'
 }