Fix some mentions to memory units in postgresql.conf.sample
The default unit for max_slot_wal_keep_size is megabytes.  While on it,
also change temp_file_limit to use a more consistent wording.
Reported-by: Jeff Janes, Fujii Masao
Author: Kyotaro Horiguchi
Discussion:
# - Disk -
#temp_file_limit = -1 # limits per-process temp file space
- # in kB, or -1 for no limit
+ # in kilobytes, or -1 for no limit
# - Kernel Resources -
#max_wal_senders = 10 # max number of walsender processes
# (change requires restart)
#wal_keep_segments = 0 # in logfile segments; 0 disables
-#max_slot_wal_keep_size = -1 # measured in bytes; -1 disables
+#max_slot_wal_keep_size = -1 # in megabytes; -1 disables
#wal_sender_timeout = 60s # in milliseconds; 0 disables
#max_replication_slots = 10 # max number of replication slots
