Update copyright for 2021

Backpatch-through: 9.5

src/backend/utils/sort/logtape.c

@@ -67,7 +67,7 @@
  * There will always be the same number of runs as input tapes, and the same
  * number of input tapes as participants (worker Tuplesortstates).
  *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION

src/backend/utils/sort/sharedtuplestore.c

@@ -10,7 +10,7 @@
  * scan where each backend reads an arbitrary subset of the tuples that were
  * written.
  *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION

src/backend/utils/sort/sortsupport.c

@@ -4,7 +4,7 @@
  *	  Support routines for accelerated sorting.
  *
  *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION

src/backend/utils/sort/tuplesort.c

@@ -83,7 +83,7 @@
  * produce exactly one output run from their partial input.
  *
  *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION

src/backend/utils/sort/tuplestore.c

@@ -43,7 +43,7 @@
  * before switching to the other state or activating a different read pointer.
  *
  *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION