Revert "Move windows builds to experimental to unblock release packages." (#21723)

Reverts iree-org/iree#21712

These release builds are working again thanks to
https://github.com/iree-org/iree/pull/21717. Sample successful run:
https://github.com/iree-org/iree/actions/runs/17031585155/job/48275510639.
diff --git a/.github/workflows/build_package.yml b/.github/workflows/build_package.yml
index a567a99..f9a6c88 100644
--- a/.github/workflows/build_package.yml
+++ b/.github/workflows/build_package.yml
@@ -168,7 +168,7 @@
           - runs-on: windows-2022
             build-family: windows
             build-package: py-compiler-pkg
-            experimental: true
+            experimental: false
           - runs-on: windows-2022
             build-family: windows
             build-package: py-runtime-pkg