zed: purge all mentions of a configuration file

There simply isn't a need for one, since the flags the daemon takes
are all short (mostly just toggles) and administrative in nature,
and are therefore better served by the age-old tradition of sourcing an
environment file and preparing the cmdline in the init-specific handler
itself, if needed at all

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #11834

man/man8/zed.8.in

@@ -76,9 +76,6 @@ while the daemon is running.
 .BI \-Z
 Zero the daemon's state, thereby allowing zevents still within the kernel
 to be reprocessed.
-.\" .TP
-.\" .BI \-c\  configfile
-.\" Read the configuration from the specified file.
 .TP
 .BI \-d\  zedletdir
 Read the enabled ZEDLETs from the specified directory.
@@ -203,9 +200,6 @@ the following executables are defined: \fBZDB\fR, \fBZED\fR, \fBZFS\fR,
 rc file if needed.
 
 .SH FILES
-.\" .TP
-.\" @sysconfdir@/zfs/zed.conf
-.\" The default configuration file for the daemon.
 .TP
 .I @sysconfdir@/zfs/zed.d
 The default directory for enabled ZEDLETs.
@@ -250,8 +244,6 @@ environment variables having a "_NOT_IMPLEMENTED_" value.
 .PP
 Internationalization support via gettext has not been added.
 .PP
-The configuration file is not yet implemented.
-.PP
 The diagnosis engine is not yet implemented.
 
 .SH LICENSE