add missing import

Author: kwin

plugin-maven/src/main/java/com/diffplug/spotless/maven/AbstractSpotlessMojo.java

@@ -50,6 +50,7 @@
 import org.eclipse.aether.RepositorySystem;
 import org.eclipse.aether.RepositorySystemSession;
 import org.eclipse.aether.repository.RemoteRepository;
+import org.sonatype.plexus.build.incremental.BuildContext;
 
 import com.diffplug.spotless.Formatter;
 import com.diffplug.spotless.LineEnding;