CI: Re-enable Windows VS2019 builds

The failures are fixed, but I didn't notice this had been silently
disabled in !4272.

Re-enable the VS2019 build.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4374>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4374>

.gitlab-ci.yml

@@ -259,6 +259,7 @@ windows_build_vs2019:
     - windows
     - docker
     - "1809"
+    - mesa
   cache:
     key: ${CI_JOB_NAME}
     paths:
@@ -426,7 +427,7 @@ meson-clang:
     CC: "ccache clang-9"
     CXX: "ccache clang++-9"
 
-.meson-windows-vs2019:
+meson-windows-vs2019:
   extends:
     - .build-windows
     - .use-windows_build_vs2019