Log stale lock files in verbose mode only

Actually do what the comment says is intended. wxLogInfo() and
wxLogVerbose() differ in that only the latter must be explicitly
enabled with --verbose.

src/unix/snglinst.cpp

@@ -298,7 +298,7 @@ bool wxSingleInstanceCheckerImpl::Create(const wxString& name)
                     // message is that the previous instance of the program
                     // crashed), don't show it by default, i.e. unless the
                     // program is running with --verbose command line option.
-                    wxLogInfo(_("Deleted stale lock file '%s'."),
+                    wxLogVerbose(_("Deleted stale lock file '%s'."),
                                  name.c_str());
 
                     // retry now