Remove unused File import from AbstractMavenIntegrationTestCase

The File import is no longer needed after removing the extractResources()
method. The class now exclusively uses Path for file operations.

All integration tests compile and run successfully.

Author: gnodet

its/core-it-support/maven-it-helper/src/main/java/org/apache/maven/it/AbstractMavenIntegrationTestCase.java

@@ -18,7 +18,6 @@
  */
 package org.apache.maven.it;
 
-import java.io.File;
 import java.io.FilterInputStream;
 import java.io.IOException;
 import java.io.InputStream;