Fix indentation of comment in plannodes.h

Oversight in commit 3d17d7d.  Worth noting that pgindent was fine
as-is.

Author: Sami Imseih
Discussion: https://postgr.es/m/CAA5RZ0t80hP2aTv97QtEJy39GkxKmDBVDiTBApfiuTa4O=TEWQ@mail.gmail.com

Author: michaelpq

src/include/nodes/plannodes.h

@@ -110,7 +110,7 @@ typedef struct PlannedStmt
 	 */
 	List	   *subplans;
 
-/* indices of subplans that require REWIND */
+	/* indices of subplans that require REWIND */
 	Bitmapset  *rewindPlanIDs;
 
 	/* a list of PlanRowMark's */