remove mail addresses from man pages

apparently, some people don't see the "maintained by" bits, so make them
look harder for explicit contact information (to be found in AUTHORS).

src/compat/isync.1

@@ -316,7 +316,6 @@ mbsync(1), mdconvert(1), mutt(1), maildir(5)
 .P
 Up to date information on \fBisync\fR can be found at http://isync.sf.net/
 ..
-.SH AUTHOR
-Written by Michael R. Elkins <me@mutt.org>,
-.br
-maintained by Oswald Buddenhagen <ossi@users.sf.net>.
+.SH AUTHORS
+Originally written by Michael R. Elkins,
+currently maintained by Oswald Buddenhagen.

src/mbsync.1

@@ -471,9 +471,7 @@ mdconvert(1), isync(1), mutt(1), maildir(5)
 .P
 Up to date information on \fBmbsync\fR can be found at http://isync.sf.net/
 ..
-.SH AUTHOR
-Written by Michael R. Elkins <me@mutt.org>,
-.br
-rewritten and maintained by Oswald Buddenhagen <ossi@users.sf.net>,
-.br
-contributions by Theodore Y. Ts'o <tytso@mit.edu>.
+.SH AUTHORS
+Originally written by Michael R. Elkins,
+rewritten and currently maintained by Oswald Buddenhagen,
+contributions by Theodore Y. Ts'o.