Upgrade log4j to 2.15.0 (#237)

Signed-off-by: yhmo <yihua.mo@zilliz.com>

pom.xml

@@ -145,7 +145,7 @@
         <dependency>
             <groupId>org.apache.logging.log4j</groupId>
             <artifactId>log4j-slf4j-impl</artifactId>
-            <version>2.12.1</version>
+            <version>2.15.0</version>
         </dependency>
         <dependency>
             <groupId>junit</groupId>