asyncio: Fix spelling and typos.

Thanks to Vajrasky Kok for discovering some of them.
diff --git a/Lib/asyncio/protocols.py b/Lib/asyncio/protocols.py
index 3c4f3f4..52fc25c 100644
--- a/Lib/asyncio/protocols.py
+++ b/Lib/asyncio/protocols.py
@@ -114,7 +114,7 @@
     def pipe_data_received(self, fd, data):
         """Called when the subprocess writes data into stdout/stderr pipe.
 
-        fd is int file dascriptor.
+        fd is int file descriptor.
         data is bytes object.
         """