Change deprecated jcenter() maven repo to mavenCentral()

jcenter() repo was closed by the jfrog company and operates in the read-only mode.
Gradle is also planning to deprecate this in the future releases.
For details see: https://blog.gradle.org/jcenter-shutdown

All used lib dependencies seem to be available from the mavenCentral() as well.


Signed-off-by: Veniamin Fernandes <[email protected]>

build.gradle

@@ -20,7 +20,7 @@ apply plugin: 'maven-publish'
 repositories {
     flatDir { dirs uri("${projectDir}/lib") }
     maven { url 'https://mvn.freenetproject.org' }
-    jcenter()
+    mavenCentral()
 }
 
 sourceSets {