add release date to v2.6.1

Author: Stefal

CHANGELOG.md

@@ -1,17 +1,13 @@
 # Changelog
 
-## [2.6.1] - not released
-### Added
+## [2.6.1] - 2024-08-26
 ### Changed
  - More tests before installing prebuilt RTKLib cli tools.
-### Deprecated
-### Removed
 ### Fixed
  - Build rtklib if previous installed release is not working. #418
  - Insert new release into settings.conf before restarting services. #411
  - Custom web_port setting was not used. #419
  - Cellular modem: nmcli connection was not updated after a switch to public ip address.
-### Security
 
 ## [2.6.0] - 2024-07-05
 ### Added