Doc: Apply keyword role around finally (in sys module doc)

Author: adorilson

Doc/library/sys.rst

@@ -523,7 +523,7 @@ always available. Unless explicitly noted otherwise, all variables are read-only
 
    Since :func:`exit` ultimately "only" raises an exception, it will only exit
    the process when called from the main thread, and the exception is not
-   intercepted. Cleanup actions specified by finally clauses of :keyword:`try` statements
+   intercepted. Cleanup actions specified by :keyword:`finally` clauses of :keyword:`try` statements
    are honored, and it is possible to intercept the exit attempt at an outer level.
 
    .. versionchanged:: 3.6