Remove unused (multi)channeled marker types

These were introduced to help make channels easier to typecheck in the
DFK, but the DFK code continued to use hasattr tests for 'channel' and
'channels' attributes rather than these marker types.

This is part of channel removal, issue #3515

parsl/providers/base.py

@@ -2,7 +2,6 @@
 from abc import ABCMeta, abstractmethod, abstractproperty
 from typing import Any, Dict, List, Optional
 
-from parsl.channels.base import Channel
 from parsl.jobs.states import JobStatus
 
 logger = logging.getLogger(__name__)
@@ -154,18 +153,3 @@ def status_polling_interval(self) -> int:
         :return: the number of seconds to wait between calls to status()
         """
         pass
-
-
-class Channeled():
-    """A marker type to indicate that parsl should manage a Channel for this provider"""
-    def __init__(self) -> None:
-        self.channel: Channel
-        pass
-
-
-class MultiChanneled():
-    """A marker type to indicate that parsl should manage multiple Channels for this provider"""
-
-    def __init__(self) -> None:
-        self.channels: List[Channel]
-        pass