Make spelling of cancelled/cancellation consistent

This fixes places where words derived from cancel were not using their
common en-US ugly^H^H^H^Hspelling.

Author: Jelte Fennema-Nio <postgres@jeltef.nl>
Reported-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CA+hUKG+Lrq+ty6yWXF5572qNQ8KwxGwG5n4fsEcCUap685nWvQ@mail.gmail.com

src/backend/storage/lmgr/proc.c

@@ -1353,7 +1353,7 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
 			 * coding means that there is a tiny chance that the process
 			 * terminates its current transaction and starts a different one
 			 * before we have a change to send the signal; the worst possible
-			 * consequence is that a for-wraparound vacuum is cancelled.  But
+			 * consequence is that a for-wraparound vacuum is canceled.  But
 			 * that could happen in any case unless we were to do kill() with
 			 * the lock held, which is much more undesirable.
 			 */

src/test/isolation/specs/detach-partition-concurrently-4.spec

@@ -1,6 +1,6 @@
 # This test exercises behavior of foreign keys in the face of concurrent
 # detach of partitions in the referenced table.
-# (The cases where the detaching transaction is cancelled is interesting
+# (The cases where the detaching transaction is canceled is interesting
 # because the locking situation is completely different.  I didn't verify
 # that keeping both variants adds any extra coverage.)
 #

src/test/recovery/t/001_stream_rep.pl

@@ -601,7 +601,7 @@ is( $node_primary->poll_query_until(
 ok( pump_until(
 		$sigchld_bb, $sigchld_bb_timeout,
 		\$sigchld_bb_stderr, qr/backup is not in progress/),
-	'base backup cleanly cancelled');
+	'base backup cleanly canceled');
 $sigchld_bb->finish();
 
 done_testing();