chore(deps): Update Log4J dependency to 2.21.0 (revert log4j-maven-shade-plugin-extensions not yet published)

Author: deki

samples/spring/pet-store/pom.xml

@@ -115,7 +115,7 @@
                             <dependency>
                                 <groupId>io.github.edwgiz</groupId>
                                 <artifactId>log4j-maven-shade-plugin-extensions</artifactId>
-                                <version>2.21.0</version>
+                                <version>2.20.0</version>
                             </dependency>
                         </dependencies>
                     </plugin>