Remove TcpClient.write/read shared locks

Since they were shared between write and read, and now the read
is done constantly on a separate thread, the read lock would
cause the write method to be locked and not functional at all

telethon/extensions/tcp_client.py

@@ -65,8 +65,9 @@ class TcpClient:
     def write(self, data):
         """Writes (sends) the specified bytes to the connected peer"""
 
-        # Ensure that only one thread can send data at once
-        with self._lock:
+        # TODO Check whether the code using this has multiple threads calling
+        # .write() on the very same socket. If so, have two locks, one for
+        # .write() and another for .read().
         try:
             view = memoryview(data)
             total_sent, total = 0, len(data)
@@ -95,8 +96,6 @@ class TcpClient:
            operation. Set to None for no timeout
         """
 
-        # Ensure that only one thread can receive data at once
-        with self._lock:
         # Ensure it is not cancelled at first, so we can enter the loop
         self.cancelled.clear()