Fix some minor errors in the docs (GH-24834)

diff --git a/Doc/library/asyncio-api-index.rst b/Doc/library/asyncio-api-index.rst
index 047e5bb..f558724 100644
--- a/Doc/library/asyncio-api-index.rst
+++ b/Doc/library/asyncio-api-index.rst
@@ -49,7 +49,7 @@
       - Task object.
 
     * - :func:`to_thread`
-      - Asychronously run a function in a separate OS thread.
+      - Asynchronously run a function in a separate OS thread.
 
     * - :func:`run_coroutine_threadsafe`
       - Schedule a coroutine from another OS thread.