Update README.md - code of conduct badge and link

I updated the code of conduct badge to Contributor Covenant 2.1 and also the link.
The link was broken, as the file was removed from this repository, since it is using the default provided by the GitHub org.

README.md

@@ -6,7 +6,7 @@
 
 <!-- [![Coverage Status](https://coveralls.io/repos/github/SAP/ui5-linter/badge.svg)](https://coveralls.io/github/SAP/ui5-linter) -->
 <!-- [![OpenUI5 Community Slack (#tooling channel)](https://img.shields.io/badge/slack-join-44cc11.svg)](https://ui5-slack-invite.cfapps.eu10.hana.ondemand.com/) -->
-[![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg)](CODE_OF_CONDUCT.md)
+[![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.1%20adopted-ff69b4.svg)](https://github.com/SAP/ui5-linter?tab=coc-ov-file#readme)
 <!-- [![Fosstars security rating](https://github.com/SAP/ui5-linter/blob/fosstars-report/fosstars_badge.svg)](https://github.com/SAP/ui5-linter/blob/fosstars-report/fosstars_report.md) -->
 <!-- [![REUSE status](https://api.reuse.software/badge/github.com/SAP/ui5-linter)](https://api.reuse.software/info/github.com/SAP/ui5-linter) -->