Skip testing with PyTorch 1.7 and Python 3.9 on Ubuntu (#11217)

Co-authored-by: Carlos Mocholí <carlossmocholi@gmail.com>

.github/workflows/ci_test-full.yml

@@ -21,6 +21,9 @@ jobs:
         python-version: ["3.7", "3.9"]  # minimum, maximum
         requires: ["oldest", "latest"]
         release: ["stable"]
+        exclude:
+          # Skip if torch<1.8 and py3.9 on Linux: https://github.com/pytorch/pytorch/issues/50014
+          - {os: ubuntu-18.04, python-version: "3.9", requires: "oldest", release: "stable"}
         #include:
           # nightly: add when there's a release candidate
           #- {os: ubuntu-20.04, python-version: "3.10", requires: "latest", release: "pre"}