fix roff abuse in mdconvert man page

this one was missed in a33e4475.

src/mdconvert.1

@@ -1,22 +1,21 @@
-.ig
-\" SPDX-FileCopyrightText: 2004-2022 Oswald Buddenhagen <ossi@users.sf.net>
-\" SPDX-License-Identifier: GPL-2.0-or-later
-\"
-\" mdconvert - Maildir mailbox UID storage scheme converter
-..
+.\" SPDX-FileCopyrightText: 2004-2022 Oswald Buddenhagen <ossi@users.sf.net>
+.\" SPDX-License-Identifier: GPL-2.0-or-later
+.\"
+.\" mdconvert - Maildir mailbox UID storage scheme converter
+.
 .TH mdconvert 1 "2004 Mar 27"
-..
+.
 .SH NAME
 mdconvert - Maildir mailbox UID storage scheme converter
-..
+.
 .SH SYNOPSIS
 \fBmdconvert\fR [\fIoptions\fR ...] \fImailbox\fR ...
-..
+.
 .SH DESCRIPTION
 \fBmdconvert\fR converts Maildir mailboxes between the two UID storage schemes
 supported by \fBmbsync\fR. See \fBmbsync\fR's manual page for details on these
 schemes.
-..
+.
 .SH OPTIONS
 .TP
 \fB-a\fR, \fB--alt\fR
@@ -31,9 +30,9 @@ Displays a summary of command line options.
 .TP
 \fB-v\fR, \fB--version\fR
 Displays version information.
-..
+.
 .SH SEE ALSO
 mbsync(1)
-..
+.
 .SH AUTHOR
 Written and maintained by Oswald Buddenhagen <ossi@users.sf.net>.