Remove unused parent field in PlotLane

Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>

org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java

@@ -139,7 +139,6 @@ protected void enter(final int index, final PlotCommit<L> currCommit) {
 				rObj.addPassingLane(c.lane);
 			}
 			currCommit.lane = c.lane;
-			currCommit.lane.parent = currCommit;
 		} else {
 			// More than one child, or our child is a merge.
 			// Use a different lane.
@@ -154,7 +153,6 @@ protected void enter(final int index, final PlotCommit<L> currCommit) {
 			}
 
 			currCommit.lane = nextFreeLane();
-			currCommit.lane.parent = currCommit;
 			activeLanes.add(currCommit.lane);
 
 			int remaining = nChildren;

org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotLane.java

@@ -49,8 +49,6 @@
  * Commits are strung onto a lane. For many UIs a lane represents a column.
  */
 public class PlotLane {
-	PlotCommit parent;
-
 	int position;
 
 	/**