CI/CD: revert to pre LFS external/window

.github/workflows/sdrangel.yml

@@ -30,7 +30,7 @@ jobs:
             generators: Ninja
           }
     steps:
-      - uses: nschloe/action-cached-lfs-checkout@v1
+      - uses: actions/checkout@v2
         with:
           submodules: true
           fetch-depth: 0

external/windows

@@ -1 +1 @@
-Subproject commit ad7597800190713b04a26e396de561424b42e496
+Subproject commit f20b21d50f9ef3930f6979759adc5af32f65c92a