COMP: Update CXX workflow ref to merged v5.4.6 branch

The add-apt-packages-input feature branch was merged into v5.4.6
as commit 7beece0. Update the CXX workflow ref to use the stable
branch instead of the now-stale feature branch.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hjmjohnson

.github/workflows/build-test-package.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   cxx-build-workflow:
-    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@add-apt-packages-input
+    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@v5.4.6
     with:
       apt-packages: 'libopenslide-dev'
       brew-packages: 'openslide'