upgrade log4j2 to 2.15.0 for 0-day (#39)

Author: daleiz

client/build.gradle

@@ -28,7 +28,7 @@ dependencies {
     implementation group: 'com.google.protobuf', name: 'protobuf-java-util', version: '3.17.3'
 
     compileOnly group: 'org.slf4j', name: 'slf4j-api', version: '1.7.30'
-    implementation group: 'org.apache.logging.log4j', name: 'log4j-slf4j-impl', version: '2.14.1'
+    implementation group: 'org.apache.logging.log4j', name: 'log4j-slf4j-impl', version: '2.15.0'
 
     implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.12.0'