Allow failure for the latest ONNX and TF in CI (onnx#840)

Allow failure for the latest ONNX and TF in CI

Signed-off-by: Chin Huang <[email protected]>

Author: chinhuang007

.github/workflows/test-backend.yml

@@ -6,6 +6,8 @@ jobs:
   unittest:
 
     runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ startsWith(matrix.onnx-version, 'git+') }}
+
     strategy:
       matrix:
         # Test current versions on all platforms