patch 8.1.2072: "gk" moves to start of line instead of upwards

Problem:    "gk" moves to start of line instead of upwards.
Solution:   Fix off-by-one error. (Christian Brabandt, closes #4969)
diff --git a/src/normal.c b/src/normal.c
index adc7541..4db90d6 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -3406,8 +3406,8 @@
       {
 	if (dir == BACKWARD)
 	{
-	    if ((long)curwin->w_curswant >= width2)
-		/* move back within line */
+	    if ((long)curwin->w_curswant > width2)
+		// move back within line
 		curwin->w_curswant -= width2;
 	    else
 	    {