Update daemon.py for Python 3.8 compatibility (#912)

Signed-off-by: AhmedMoaz <[email protected]>

ros2cli/ros2cli/node/daemon.py

@@ -145,7 +145,7 @@ def spawn_daemon(args, timeout=None, debug=False):
             with open('/proc/self/status', 'r') as f:
                 for line in f:
                     if line.startswith(string_to_find):
-                        fdlimit = int(line.removeprefix(string_to_find).strip())
+                        fdlimit = int(line[len(string_to_find):].strip())
                         break
         except (FileNotFoundError, ValueError):
             pass