Revert "CI: Disable Windows jobs"

They're fixed now, just in time.

This reverts commit 7b44e7d7bb.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13708>

.gitlab-ci.yml

@@ -553,7 +553,7 @@ debian/arm_test:
     MESA_IMAGE_TAG: "2021-06-24-zink-msvc"
     MESA_UPSTREAM_IMAGE: "$CI_REGISTRY/$FDO_UPSTREAM_REPO/$MESA_IMAGE_PATH:${MESA_IMAGE_TAG}"
 
-.windows_build_vs2019:
+windows_build_vs2019:
   extends:
     - .container
     - .windows-docker-vs2019
@@ -1018,7 +1018,7 @@ debian-clang:
     CC: clang
     CXX: clang++
 
-.windows-vs2019:
+windows-vs2019:
   extends:
     - .build-windows
     - .use-windows_build_vs2019
@@ -1031,7 +1031,7 @@ debian-clang:
       - _build/meson-logs/*.txt
       - _install/
 
-.test-d3d12-windows:
+test-d3d12-windows:
   extends:
     - .build-windows
     - .use-windows_build_vs2019