[CODEOWNERS] Remove invalid owner (#53982)

The focus of these changes is to remove an owner being flagged as no longer valid by the linter

Author: jsquire

.github/CODEOWNERS

@@ -1085,10 +1085,7 @@
 /sdk/pineconevectordb/Azure.ResourceManager.*/                     @ArcturusZhang @ArthurMa1978
 
 # PRLabel: %Planetary Computer
-/sdk/planetarycomputer/Azure.ResourceManager.*/                    @shaktichetan23 @ArthurMa1978
-
-# ServiceLabel: %Planetary Computer %Mgmt
-# ServiceOwners:                                                   @shaktichetan23
+/sdk/planetarycomputer/Azure.ResourceManager.*/                    @ArcturusZhang @ArthurMa1978
 
 # PRLabel: %PureStorage
 /sdk/purestorageblock/Azure.ResourceManager.*/                     @ArthurMa1978 @ArcturusZhang