Bug#1027691: Mention PSEUDO-HEADER needs colon or will silently fail

[Dan Jacobson <jidanni@jidanni.org>]

Package: reportbug
Version: 11.6.0
Severity: minor
File: /usr/share/man/man1/reportbug.1.gz
X-Debbugs-No-Ack:

At
       -P PSEUDO-HEADER, --pseudo-header=PSEUDO-HEADER
Mention a colon needs to be present.   --pseudo-header='Zzzzz' will
silently fail.

And also if there is a colon at the end, the program shouldn't add a
blank after it. Because there isn't anything to separate, so it just
becomes a trailing blank.