debugdiscovery: drop reference to non-existent --serverlog option

It seems like it didn't even exist when debugdiscovery was introduced
in cb98fed52495 (discovery: add new set-based discovery, 2011-05-02).

Differential Revision: https://phab.mercurial-scm.org/D1692

mercurial/debugcommands.py

@@ -782,25 +782,9 def debugdiscovery(ui, repo, remoteurl="
         elif rheads <= common:
             ui.write(("remote is subset\n"))
 
-    serverlogs = opts.get('serverlog')
-    if serverlogs:
-        for filename in serverlogs:
-            with open(filename, 'r') as logfile:
-                line = logfile.readline()
-                while line:
-                    parts = line.strip().split(';')
-                    op = parts[1]
-                    if op == 'cg':
-                        pass
-                    elif op == 'cgss':
-                        doit(parts[2].split(' '), parts[3].split(' '))
-                    elif op == 'unb':
-                        doit(parts[3].split(' '), parts[2].split(' '))
-                    line = logfile.readline()
-    else:
         remoterevs, _checkout = hg.addbranchrevs(repo, remote, branches,
                                                  opts.get('remote_head'))
-        localrevs = opts.get('rev')
+    localrevs = opts['rev']
         doit(localrevs, remoterevs)
 
 @command('debugextensions', cmdutil.formatteropts, [], norepo=True)