Bump com.diffplug.spotless:spotless-maven-plugin from 3.3.0 to 3.4.0 (#24)

Author: dependabot[bot]

pom.xml

@@ -376,7 +376,7 @@
             <plugin>
                 <groupId>com.diffplug.spotless</groupId>
                 <artifactId>spotless-maven-plugin</artifactId>
-                <version>3.3.0</version>
+                <version>3.4.0</version>
                 <configuration>
                     <java>
                         <!-- Use Google Java Format -->