upgrade log4j

Author: Anna Urbala

README.md

@@ -9,7 +9,7 @@ Connector supports only STRING types.
 ## Prerequisites
 * Java 11
 * Maven 3
-* Flink 15+
+* Flink 1.15+
 
 ## Implementation
 Implementation is based on Flink's `TableFunction` and `AsyncTableFunction` classes.  

pom.xml

@@ -43,7 +43,7 @@ under the License.
     <scala.binary.version>2.12</scala.binary.version>
     <maven.compiler.source>${target.java.version}</maven.compiler.source>
     <maven.compiler.target>${target.java.version}</maven.compiler.target>
-    <log4j.version>2.14.1</log4j.version>
+    <log4j.version>2.17.2</log4j.version>
     <lombok.version>1.18.22</lombok.version>
     <junit.jupiter.version>5.8.1</junit.jupiter.version>
     <json.path.version>2.6.0</json.path.version>