Add Piotr as approver.

README.md

@@ -118,6 +118,7 @@ you're more than welcome to participate!
 ([@open-telemetry/dotnet-approvers](https://github.com/orgs/open-telemetry/teams/dotnet-approvers)):
 
 * [Cijo Thomas](https://github.com/cijothomas), Microsoft
+* [Piotr Kiełkowicz](https://github.com/Kielek), Splunk
 * [Reiley Yang](https://github.com/reyang), Microsoft
 * [Utkarsh Umesan Pillai](https://github.com/utpilla), Microsoft
 * [Vishwesh Bankwar](https://github.com/vishweshbankwar), Microsoft
@@ -126,7 +127,6 @@ you're more than welcome to participate!
 ([@open-telemetry/dotnet-triagers](https://github.com/orgs/open-telemetry/teams/dotnet-triagers)):
 
 * [Martin Thwaites](https://github.com/martinjt), Honeycomb
-* [Piotr Kiełkowicz](https://github.com/Kielek), Splunk
 
 [Emeritus
 Maintainer/Approver/Triager](https://github.com/open-telemetry/community/blob/main/community-membership.md#emeritus-maintainerapprovertriager):