PEP 672: Mention Unicode TR 55 (GH-4133)

Unicode Technical Report 55 “Unicode Source Code Handling” was published in January and contains lots of relevant information and general recommendations.

Also in this PR: Yank obsolete metadata.

peps/pep-0672.rst

@@ -3,7 +3,6 @@ Title: Unicode-related Security Considerations for Python
 Author: Petr Viktorin <[email protected]>
 Status: Active
 Type: Informational
-Content-Type: text/x-rst
 Created: 01-Nov-2021
 Post-History: 01-Nov-2021
 
@@ -40,7 +39,8 @@ This document purposefully does not give any solutions
 or recommendations: it is rather a list of things to keep in mind.
 
 This document is specific to Python.
-For general security considerations in Unicode text, see [tr36]_ and [tr39]_.
+For general security considerations in Unicode text and source code,
+see Unicode technical reports [tr36]_, [tr39]_, and [tr55]_.
 
 
 Acknowledgement
@@ -379,6 +379,8 @@ References
    http://www.unicode.org/reports/tr36/
 .. [tr39]   Unicode® Technical Standard #39: Unicode Security Mechanisms
    http://www.unicode.org/reports/tr39/
+.. [tr55]  Unicode Technical Report #55: Unicode Source Code Handling
+   http://www.unicode.org/reports/tr55/
 .. _CVE-2021-42574:
    https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-42574
 .. _`Encoding declarations`: https://docs.python.org/3/reference/lexical_analysis.html#encoding-declarations
@@ -391,15 +393,3 @@ Copyright
 
 This document is placed in the public domain or under the
 CC0-1.0-Universal license, whichever is more permissive.
-
-
-
-..
-    Local Variables:
-    mode: indented-text
-    indent-tabs-mode: nil
-    sentence-end-double-space: t
-    fill-column: 70
-    coding: utf-8
-    End:
-