region: drop leftover reference to the mailing list
As per [1], the mailing list isn't used anymore.
[1]:
Fixes: ("region: stabilize interface")
* the layout and size of structs used by wlroots may change, requiring code
* depending on this header to be recompiled (but not edited).
*
- * Breaking changes are announced by email and follow a 1-year deprecation
- * schedule. Send an email to ~sircmpwn/wlroots-announce+subscribe@lists.sr.ht
- * to receive these announcements.
+ * Breaking changes are announced in the release notes and follow a 1-year
+ * deprecation schedule.
*/
#ifndef WLR_TYPES_WLR_REGION_H
