use portable provider allowlist path in manpage

spotted by Jann Horn

Author: djmdjm

ssh-agent.1

@@ -156,7 +156,7 @@ See PATTERNS in
 .Xr ssh_config 5
 for a description of pattern-list syntax.
 The default list is
-.Dq /usr/lib/*,/usr/local/lib/* .
+.Dq usr/lib*/*,/usr/local/lib*/* .
 .It Fl s
 Generate Bourne shell commands on
 .Dv stdout .