qtplasmac: change updater to only unlink qtplasmac symlink

Previously we deleted the (empty) qtplasmac folder if it existed as 
well.  Due to how qtvcp copy works, the folder needs to exist, and an 
empty one (from an old config) really doesnt matter.
This fixes the issue described by Samas322 in this thread: 
https://forum.linuxcnc.org/plasmac/49311-qtvcp-copy-error#273305

Author: snowgoer540

share/qtvcp/screens/qtplasmac/qtplasmac_handler.py

@@ -2378,16 +2378,13 @@ def update_check(self):
         if 'metric_startup' in startupCode or 'imperial_startup' in startupCode:
             self.updateIni.append(207)
         # remove the qtplasmac link from the config directory (pre V1.225.208 2022/06/29)
-        if os.path.lexists(os.path.join(self.PATHS.CONFIGPATH, 'qtplasmac')):
+        if os.path.islink(os.path.join(self.PATHS.CONFIGPATH, 'qtplasmac')):
             # stage 1: set up for unlinking on the next run of qtplasmac
             if 'code.py' in self.iniFile.find('FILTER', 'ngc'):
                 self.updateIni.append(208)
             # stage 2: remove the qtplasmac link
             else:
-                if os.path.islink(os.path.join(self.PATHS.CONFIGPATH, 'qtplasmac')):
-                    os.unlink(os.path.join(self.PATHS.CONFIGPATH, 'qtplasmac'))
-                else:
-                    os.rmdir(os.path.join(self.PATHS.CONFIGPATH, 'qtplasmac'))
+                os.unlink(os.path.join(self.PATHS.CONFIGPATH, 'qtplasmac'))
         # move qtplasmac options from INI file to prefs file pre V1.227.219 2022/07/14)
         if not self.PREFS.has_section('BUTTONS'):
             UPDATER.move_options_to_prefs_file(self.iniFile, self.PREFS)