Upgrade fmt-maven-plugin 2.18 -> 2.21.1

See:
- https://github.com/spotify/fmt-maven-plugin/releases/tag/2.21.1
- https://github.com/spotify/fmt-maven-plugin/releases/tag/2.21
- spotify/fmt-maven-plugin@2.18.0...2.19.0

pom.xml

@@ -258,7 +258,7 @@
                 <plugin>
                     <groupId>com.spotify.fmt</groupId>
                     <artifactId>fmt-maven-plugin</artifactId>
-                    <version>2.18</version>
+                    <version>2.21.1</version>
                     <configuration>
                         <forkMode>never</forkMode>
                     </configuration>