Update TESTOWNERS (#9153)

Author: naspirato

.github/TESTOWNERS

@@ -18,11 +18,9 @@
 #Column Tables Development Team @zverevgeny TEAM:@ydb-platform/cs
 /ydb/core/tx/columnshard @ydb-platform/cs
 
-
 #Distributed System Infrastructure Team @ijon TEAM:@ydb-platform/system-infra
 /ydb/core/mind/hive @ydb-platform/system-infra
 /ydb/core/tx/schemeshard @ydb-platform/system-infra
-/ydb/core/tx/columnshard @ivanmorozov333 @ydb-platform/system-infra
 /ydb/core/util @ydb-platform/system-infra
 /ydb/core/client @ydb-platform/system-infra
 /ydb/core/engine @ydb-platform/system-infra