net-im/py-matrix-synapse: Update 1.135.0 => 1.138.0 (security)

Changelogs:
https://github.com/element-hq/synapse/blob/v1.138.0/CHANGES.md

This release includes support for room version 12 which fixes a number
of security vulnerabilities, including CVE-2025-49090.

While here fix warnings from portclippy, sort DOCS, improve indents.

PR: 289253
Approved by: Sascha Biberhofer <ports@skyforge.at> (maintainer, timeout 2 weeks)
Security: CVE-2025-49090
MFH: 2025Q3

(cherry picked from commit c460176f75937d72b18ef3b65b329b5301e85a84)