Remove unused function

src/tempus/Tempus.py

@@ -124,17 +124,6 @@ class Tempus(Device):
             last_time = actual_time
             await sleep(1)
 
-    def clean_stderr(self, msg):
-        """Strip harmless lines from stderr"""
-        clean_msg = ""
-        for line in msg.splitlines():
-            if "X11 forwarding request failed" in line:
-                continue  # harmless
-            elif "WARNING:root:Didn't read back" in line:
-                continue  # harmless
-            clean_msg += line + '\n'
-        return clean_msg
-
     controllerIp = String(
         displayedName="Controller IP",
         defaultValue="169.254.1.5",