[Concurrency] ignore @_marker protocol AnyActor ABI warnings

These are not an issue because adding a @_marker protocol conformance has no ABI impact - the protocol is not available at runtime.

Author: ktoso

test/api-digester/stability-concurrency-abi.test

@@ -58,5 +58,7 @@ Func AsyncSequence.map(_:) is now with @preconcurrency
 Func AsyncSequence.prefix(while:) is now with @preconcurrency
 Func MainActor.run(resultType:body:) has generic signature change from <T where T : Swift.Sendable> to <T>
 Func MainActor.run(resultType:body:) has mangled name changing from 'static Swift.MainActor.run<A where A: Swift.Sendable>(resultType: A.Type, body: @Swift.MainActor @Sendable () throws -> A) async throws -> A' to 'static Swift.MainActor.run<A>(resultType: A.Type, body: @Swift.MainActor @Sendable () throws -> A) async throws -> A'
+Protocol Actor has added inherited protocol AnyActor
+Protocol Actor has generic signature change from <Self : AnyObject, Self : Swift.Sendable> to <Self : _Concurrency.AnyActor>
 Struct CheckedContinuation has removed conformance to UnsafeSendable
 // *** DO NOT DISABLE OR XFAIL THIS TEST. *** (See comment above.)