Skip ONNX group normalization tests on CPU.

They were already skipped on GPU. They seem to be flaky... or otherwise broken in some weird way.

build_tools/pkgci/external_test_suite/onnx_cpu_llvm_sync.json

diff --git a/build_tools/pkgci/external_test_suite/onnx_cpu_llvm_sync.json b/build_tools/pkgci/external_test_suite/onnx_cpu_llvm_sync.json
index 227af74..0dc88ab 100644
--- a/build_tools/pkgci/external_test_suite/onnx_cpu_llvm_sync.json
+++ b/build_tools/pkgci/external_test_suite/onnx_cpu_llvm_sync.json
@@ -8,7 +8,9 @@
     "--device=local-sync"
   ],
   "skip_compile_tests": [
-    "onnx/node/generated/test_dequantizelinear"
+    "onnx/node/generated/test_dequantizelinear",
+    "onnx/node/generated/test_group_normalization_epsilon_expanded",
+    "onnx/node/generated/test_group_normalization_example_expanded"
   ],
   "skip_run_tests": [],
   "expected_compile_failures": [