Adjust Log4j2 version in README.md

Author: KarstenSchnitter

README.md

@@ -110,12 +110,12 @@ Again, we don't include dependencies to those implementation backends ourselves,
 <dependency>
 	<groupId>org.apache.logging.log4j</groupId>
 	<artifactId>log4j-slf4j-impl</artifactId>
-	<version>2.8.2</version>
+	<version>2.15.0</version>
 </dependency>
 	<dependency>
 	<groupId>org.apache.logging.log4j</groupId>
 	<artifactId>log4j-core</artifactId>
-	<version>2.8.2</version>
+	<version>2.15.0</version>
 </dependency>
 ```
 
@@ -320,4 +320,4 @@ More info on the actual implementation can be found in the [Wiki](https://github
 
 ## Licensing
 
-Please see our [LICENSE](LICENSE) for copyright and license information. Detailed information including third-party components and their licensing/copyright information is available via the [REUSE](https://api.reuse.software/info/github.com/SAP/cf-java-logging-support) tool.
+Please see our [LICENSE](LICENSE) for copyright and license information. Detailed information including third-party components and their licensing/copyright information is available via the [REUSE](https://api.reuse.software/info/github.com/SAP/cf-java-logging-support) tool.