Fix cursor moving down when selection exist. Solves (zyedidia#3087) (zyedidia#3091)

Previously `CursorDown` function called `Deselect` with a wrong
argument which lead to the situation when cursor was moved to the
start instead of the end of the selection

Signed-off-by: Yevhen Babiichuk (DustDFG) <[email protected]>

Author: dustdfg

internal/action/actions.go

@@ -209,7 +209,7 @@ func (h *BufPane) CursorUp() bool {
 
 // CursorDown moves the cursor down
 func (h *BufPane) CursorDown() bool {
-	h.Cursor.Deselect(true)
+	h.Cursor.Deselect(false)
 	h.MoveCursorDown(1)
 	h.Relocate()
 	return true