(index) Improve disk locality of the positions data

code/index/index-reverse/java/nu/marginalia/index/construction/PositionsFileConstructor.java

@@ -23,13 +23,9 @@ import java.nio.file.StandardOpenOption;
  * each posting in the file.
  */
 public class PositionsFileConstructor implements AutoCloseable {
-    private final int BLOCK_SIZE = 4096;
-    
     private final Path file;
     private final FileChannel channel;
 
-    private long offset;
-
     public PositionsFileConstructor(Path file) throws IOException {
         this.file = file;