[Python] Drop network lock

The network lock is not needed in the Python controller, as all calls
to the SDK are made by posting to the Matter SDK event loop through
ScheduleWork(), hence are guaranteed to be serialized.

From how I understand ScheduleWork() works, it pushes the work to the
event loop through PostEvent() which at least on POSIX is using the
thread safe device queue (see GenericPlatformManagerImpl_POSIX.cpp).

src/controller/python/chip/ChipStack.py

@@ -144,8 +144,6 @@ class ChipStack(object):
     def __init__(self, persistentStoragePath: str, enableServerInteractions=True):
         builtins.enableDebugMode = False
 
-        # TODO: Probably no longer necessary, see https://github.com/project-chip/connectedhomeip/issues/33321.
-        self.networkLock = Lock()
         self.completeEvent = Event()
         self.commissioningCompleteEvent = Event()
         self._ChipStackLib = None
@@ -212,7 +210,6 @@ def Shutdown(self):
         # #20437 tracks consolidating these.
         #
         self._ChipStackLib.pychip_CommonStackShutdown()
-        self.networkLock = None
         self.completeEvent = None
         self._ChipStackLib = None
         self._chipDLLPath = None
@@ -226,10 +223,7 @@ def Call(self, callFunct, timeoutMs: int = None):
         This function is a wrapper of PostTaskOnChipThread, which includes some handling of application specific logics.
         Calling this function on CHIP on CHIP mainloop thread will cause deadlock.
         '''
-        # TODO: Lock probably no longer necessary, see https://github.com/project-chip/connectedhomeip/issues/33321.
-        with self.networkLock:
-            res = self.PostTaskOnChipThread(callFunct).Wait(timeoutMs)
-        return res
+        return self.PostTaskOnChipThread(callFunct).Wait(timeoutMs)
 
     async def CallAsync(self, callFunct, timeoutMs: int = None):
         '''Run a Python function on CHIP stack, and wait for the response.
@@ -256,9 +250,7 @@ def CallAsyncWithCompleteCallback(self, callFunct):
         # throw error if op in progress
         self.callbackRes = None
         self.completeEvent.clear()
-        # TODO: Lock probably no longer necessary, see https://github.com/project-chip/connectedhomeip/issues/33321.
-        with self.networkLock:
-            res = self.PostTaskOnChipThread(callFunct).Wait()
+        res = self.PostTaskOnChipThread(callFunct).Wait()
 
         if not res.is_success:
             self.completeEvent.set()