PEP 553: Fix citation references (#2639)

* PEP 553: Remove orphaned citation to fix build warning

* PEP 553: Remove redundant emacs metadata

Author: hugovk

pep-0553.rst

@@ -280,22 +280,8 @@ References
 .. [impl]
    https://github.com/python/cpython/pull/3355
 
-.. [envar]
-   https://mail.python.org/pipermail/python-dev/2017-September/149447.html
-
 
 Copyright
 =========
 
 This document has been placed in the public domain.
-
-
-
-..
-   Local Variables:
-   mode: indented-text
-   indent-tabs-mode: nil
-   sentence-end-double-space: t
-   fill-column: 70
-   coding: utf-8
-   End: