docs: update changelog headers for date and compare link fixes (#409)

[\[MOB-13257\] \[CP\] \[FLT\] Update changelog with missing dates and version comparison links - JIRA](https://instabug.atlassian.net/browse/MOB-13257)

Author: abdelhamid-f-nasser

CHANGELOG.md

@@ -11,7 +11,7 @@
 
 - Re-enable screenshot capturing for Crash Reporting and Session Replay by removing redundant mapping ([#407](https://github.com/Instabug/Instabug-Flutter/pull/407)). 
 
-## [12.1.0](https://github.com/Instabug/Instabug-Flutter/compare/v12.1.0...v11.14.0)
+## [12.1.0](https://github.com/Instabug/Instabug-Flutter/compare/v11.14.0...v12.1.0) (September, 28, 2023)
 
 ### Added