Remove deprecated File-based loadFile() method from Verifier

The loadFile(File, boolean) method is no longer needed as all callers
have been migrated to use the Path-based loadFile(Path, boolean) method
or the String-based convenience method.

This further reduces the File API surface in the integration test
infrastructure, completing the migration to NIO2 Path API.

Author: gnodet

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

@@ -572,10 +572,6 @@ public List<String> loadFile(String basedir, String filename, boolean hasCommand
         return loadFile(Paths.get(basedir).resolve(filename), hasCommand);
     }
 
-    public List<String> loadFile(File file, boolean hasCommand) throws VerificationException {
-        return loadFile(file.toPath(), hasCommand);
-    }
-
     /**
      * Loads the lines of the specified file.
      *