Fix formatting errors in page cross references

These pages had errors such as

    .BR page (x) .

which should be

    .BR page (x).

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

disk-utils/swaplabel.8

@@ -53,7 +53,7 @@ will truncate it and print a warning message.
 Specify a new \fIUUID\fR for the device.
 The \fI UUID\fR
 must be in the standard 8-4-4-4-12 character format, such as is output by
-.BR uuidgen (1) .
+.BR uuidgen (1).
 .PP
 .SH AUTHOR
 .B swaplabel

misc-utils/findmnt.8

@@ -162,7 +162,7 @@ or \fB\-\-first\-only\fP options.
 The standard columns always use the new version of the information from the
 mountinfo file, except the umount action which is based on the original
 information cached by
-.BR findmnt (8) .
+.BR findmnt (8).
 The poll mode allows to use extra columns:
 .RS
 .TP

sys-utils/blkdiscard.8

@@ -13,7 +13,7 @@ blkdiscard \- discard sectors on a device
 .B blkdiscard
 is used to discard device sectors.  This is useful for solid-state
 drivers (SSDs) and thinly-provisioned storage.  Unlike
-.BR fstrim (8) ,
+.BR fstrim (8),
 this command is used directly on the block device.
 .PP
 By default,

sys-utils/dmesg.1

@@ -120,7 +120,7 @@ Print the raw message buffer, i.e. do not strip the log-level prefixes.
 Note that the real raw format depends on the method how
 .BR dmesg (1)
 reads kernel messages.  The /dev/kmsg device uses a different format than
-.BR syslog (2) .
+.BR syslog (2).
 For backward compatibility,
 .BR dmesg (1)
 returns data always in the