Drop "3.10".

Per isl-org/Open3D#4535

Needs better workaround to test all other functionality in 3.10

Author: daavoo

.github/workflows/pyncloud_ci.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.7, 3.8, 3.9, "3.10"]
+        python-version: [3.7, 3.8, 3.9]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}