dpkg(1): Comment out documentation about disabled --command-fd option

The code for this option is currently disabled, because it has some
serious problems, once the code has been fixed the documentation can
come back.

Closes: #685677

debian/changelog

@@ -10,6 +10,8 @@ dpkg (1.16.9) UNRELEASED; urgency=low
   [ Guillem Jover ]
   * Use “statoverrides” instead of “statusoverrides” in dpkg-statoverride.
     Closes: #686995
+  * Comment out dpkg(1) documentation about disabled --command-fd option.
+    Closes: #685677
 
   [ Updated programs translations ]
   * Czech (Miroslav Kure).

man/dpkg.1

@@ -287,11 +287,11 @@ version: \fBlt le eq ne ge gt\fP. These treat an empty version as later
 than any version: \fBlt\-nl le\-nl ge\-nl gt\-nl\fP. These are provided
 only for compatibility with control file syntax: \fB< << <= = >= >>
 >\fP.
-.TP
-.B \-\-command\-fd \fIn\fP
-Accept a series of commands on input file descriptor \fIn\fP. Note:
-additional options set on the command line, and through this file descriptor,
-are not reset for subsequent commands executed during the same run.
+.\" .TP
+.\" .B \-\-command\-fd \fIn\fP
+.\" Accept a series of commands on input file descriptor \fIn\fP. Note:
+.\" additional options set on the command line, and through this file descriptor,
+.\" are not reset for subsequent commands executed during the same run.
 .TP
 .BR \-? ", " \-\-help
 Display a brief help message.