CI: Re-enable LDC Windows jobs

It works just fine, even if we can't test with DMD,
it's enough to give us coverage on the platform.

Author: Geod24

.github/workflows/main.yml

@@ -24,10 +24,10 @@ jobs:
             - { os: macos-latest,   dc: ldc-latest }
             - { os: ubuntu-latest,  dc: dmd-latest }
             - { os: ubuntu-latest,  dc: ldc-latest }
+            # DMD is dumb and seems to overwrite the LIB env variable:
             # https://github.com/dlang/dub/issues/1914
-            # https://github.com/dlang/dub/issues/1915
             # - { os: windows-latest, dc: dmd-latest }
-            # - { os: windows-latest, dc: ldc-latest }
+            - { os: windows-latest, dc: ldc-latest }
 
     runs-on: ${{ matrix.os }}
     timeout-minutes: 30