[CODEOWNERS] Remove invalid owner (Azure#47388)

* [CODEOWNERS] Remove invalid owner

The focus of these changes is to remove an invalid owner flagged by the linter.

* Update .github/CODEOWNERS

Author: jsquire

.github/CODEOWNERS

@@ -544,10 +544,10 @@
 # ServiceOwners:                                                   @aim-for-better @idear1203 @deshriva
 
 # PRLabel: %Health Deidentification
-/sdk/healthdataaiservices/                                         @GrahamMThomas
+/sdk/healthdataaiservices/                                         @alexathomases
 
 # ServiceLabel: %Health Deidentification
-# ServiceOwners:                                                   @GrahamMThomas
+# ServiceOwners:                                                   @alexathomases
 
 # ServiceLabel: %HPC Cache
 # ServiceOwners:                                                   @romahamu @omzevall