GEODE-5001: Update log4j dependency

- Since Geode has also updated to 2.11.0 now (from 2.8.x)
diff --git a/gradle.properties b/gradle.properties
index 4dc8246..15aeb54 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -27,5 +27,5 @@
 awaitilityVersion = 1.7.0
 junitVersion = 4.12
 mockitocoreVersion = 1.10.19
-log4jVersion = 2.7
+log4jVersion = 2.11.0
 systemrulesVersion = 1.16.1