Tidy up unused CVS markers in header files

The IDENTIFICATION stanza in the source files is of questionable
usefulness, but unexpanded CVS keywords that never existed in the
codebase where the expansion happened are even less useful.
Replace with the filepath to make these headers consistent with
upstream.

src/include/access/bitmap.h

@@ -6,7 +6,7 @@
  * Copyright (c) 2006-2008, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	$PostgreSQL$
+ *	src/include/access/bitmap.h
  *
  *-------------------------------------------------------------------------
  */

src/include/utils/resscheduler.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: $
+ *	  src/include/utils/resscheduler.h
  *
  *-------------------------------------------------------------------------
  */