Add 1.26.7 release notes to CHANGES.rst on main
+1.26.7 (2021-09-22)
+===================
+
+* Fixed a bug with HTTPS hostname verification involving IP addresses and lack
+ of SNI. (Issue #2400)
+* Fixed a bug where IPv6 braces weren't stripped during certificate hostname
+ matching. (Issue #2240)
+
+
1.26.6 (2021-06-25)
===================
