[clang][Module][AIX] Mark test unsupported since objc doesn't have xcoff support
Fixed error
```
Command Output (stderr):
--
fatal error: error in backend: Objective-C support is unimplemented for object file format
```
Source code in `clang/lib/CodeGen/CGObjCMac.cpp:5080`
```
case llvm::Triple::Wasm:
case llvm::Triple::GOFF:
case llvm::Triple::SPIRV:
case llvm::Triple::XCOFF:
case llvm::Triple::DXContainer:
llvm::report_fatal_error(
"Objective-C support is unimplemented for object file format");
}
```
Reviewed By: hubert.reinterpretcast
Differential Revision: https://reviews.llvm.org/D135848