Fix spelling mistake: endponts -> endpoints

Fixes https://github.com/matrix-org/matrix-doc/issues/1677

changelogs/client_server/newsfragments/1838.clarification

@@ -0,0 +1 @@
+Fix various spelling mistakes throughout the specification.

changelogs/client_server/newsfragments/1860.clarification

@@ -0,0 +1 @@
+Fix various spelling mistakes throughout the specification.

specification/client_server_api.rst

@@ -73,7 +73,7 @@ MUST be encoded as UTF-8. Clients are authenticated using opaque
 ``access_token`` strings (see `Client Authentication`_ for details), passed as a
 query string parameter on all requests.
 
-The names of the API endponts for the HTTP transport follow a convention of
+The names of the API endpoints for the HTTP transport follow a convention of
 using underscores to separate words (for example ``/delete_devices``). The key
 names in JSON objects passed over the API also follow this convention.