#11785: fix the :mod: references in email package submodule titles.

Doc/library/email.charset.rst

-:mod:`email`: Representing character sets
------------------------------------------
+:mod:`email.charset`: Representing character sets
+-------------------------------------------------
 
 .. module:: email.charset
    :synopsis: Character Sets

Doc/library/email.encoders.rst

-:mod:`email`: Encoders
-----------------------
+:mod:`email.encoders`: Encoders
+-------------------------------
 
 .. module:: email.encoders
    :synopsis: Encoders for email message payloads.

Doc/library/email.errors.rst

-:mod:`email`: Exception and Defect classes
-------------------------------------------
+:mod:`email.errors`: Exception and Defect classes
+-------------------------------------------------
 
 .. module:: email.errors
    :synopsis: The exception classes used by the email package.

Doc/library/email.generator.rst

-:mod:`email`: Generating MIME documents
----------------------------------------
+:mod:`email.generator`: Generating MIME documents
+-------------------------------------------------
 
 .. module:: email.generator
    :synopsis: Generate flat text email messages from a message structure.

Doc/library/email.header.rst

-:mod:`email`: Internationalized headers
----------------------------------------
+:mod:`email.header`: Internationalized headers
+----------------------------------------------
 
 .. module:: email.header
    :synopsis: Representing non-ASCII headers

Doc/library/email.iterators.rst

-:mod:`email`: Iterators
------------------------
+:mod:`email.iterators`: Iterators
+---------------------------------
 
 .. module:: email.iterators
    :synopsis: Iterate over a  message object tree.

Doc/library/email.message.rst

-:mod:`email`: Representing an email message
--------------------------------------------
+:mod:`email.message`: Representing an email message
+---------------------------------------------------
 
 .. module:: email.message
    :synopsis: The base class representing email messages.

Doc/library/email.mime.rst

-:mod:`email`: Creating email and MIME objects from scratch
-----------------------------------------------------------
+:mod:`email.mime`: Creating email and MIME objects from scratch
+---------------------------------------------------------------
 
 .. module:: email.mime
    :synopsis: Build MIME messages.

Doc/library/email.parser.rst

-:mod:`email`: Parsing email messages
-------------------------------------
+:mod:`email.parser`: Parsing email messages
+-------------------------------------------
 
 .. module:: email.parser
    :synopsis: Parse flat text email messages to produce a message object structure.

Doc/library/email.util.rst

-:mod:`email`: Miscellaneous utilities
--------------------------------------
+:mod:`email.utils`: Miscellaneous utilities
+-------------------------------------------
 
 .. module:: email.utils
    :synopsis: Miscellaneous email package utilities.