bpo-38872: Document exec symbol for codeop.compile_command (GH-20047)

* Document exec symbol for codeop.compile_command

* Remove extra statements

Co-authored-by: nanjekyejoannah <joannah.nanjekye@ibm.com>
diff --git a/Doc/library/codeop.rst b/Doc/library/codeop.rst
index a52d2c6..c66b9d3 100644
--- a/Doc/library/codeop.rst
+++ b/Doc/library/codeop.rst
@@ -43,8 +43,9 @@
    :exc:`OverflowError` or :exc:`ValueError` if there is an invalid literal.
 
    The *symbol* argument determines whether *source* is compiled as a statement
-   (``'single'``, the default) or as an :term:`expression` (``'eval'``).  Any
-   other value will cause :exc:`ValueError` to  be raised.
+   (``'single'``, the default), as a sequence of statements (``'exec'``) or
+   as an :term:`expression` (``'eval'``).  Any other value will
+   cause :exc:`ValueError` to  be raised.
 
    .. note::