remove redundant code

Author: the-higgs

jupyter_server/services/kernels/kernelmanager.py

@@ -201,7 +201,6 @@ async def start_kernel(self, kernel_id=None, path=None, **kwargs):
             ).inc()
 
         else:
-            self._check_kernel_id(kernel_id)
             self.log.info("Using existing kernel: %s" % kernel_id)
 
         # Initialize culling if not already