ci: Switch to MSVC's installation of vcpkg

This setup reflects a minimal build environment on Windows when both
CMake and vcpkg are vendored by MSVC.
Also, MSVC's installation of vcpkg might be a few months behind the
master branch.

.github/workflows/ci.yml

@@ -163,7 +163,7 @@ jobs:
 
       - name: Using vcpkg with MSBuild
         run: |
-          Set-Location "$env:VCPKG_INSTALLATION_ROOT"
+          Set-Location "$env:VCPKG_ROOT"
           Add-Content -Path "triplets\x64-windows.cmake" -Value "set(VCPKG_BUILD_TYPE release)"
           Add-Content -Path "triplets\x64-windows-static.cmake" -Value "set(VCPKG_BUILD_TYPE release)"
 
@@ -184,11 +184,11 @@ jobs:
         # While the vcpkg.json file includes packages with pinned versions,
         # we need to maintain its "builtin-baseline" field.
         run: |
-          & "$env:VCPKG_INSTALLATION_ROOT\vcpkg.exe" x-update-baseline --dry-run
+          & "$env:VCPKG_ROOT\vcpkg.exe" x-update-baseline --dry-run
 
       - name: Generate build system
         run: |
-          cmake -B build --preset vs2022-static -DCMAKE_TOOLCHAIN_FILE="$env:VCPKG_INSTALLATION_ROOT\scripts\buildsystems\vcpkg.cmake" -DBUILD_GUI=ON -DWITH_BDB=ON -DWITH_ZMQ=ON -DBUILD_BENCH=ON -DBUILD_FUZZ_BINARY=ON -DWERROR=ON
+          cmake -B build --preset vs2022-static -DBUILD_GUI=ON -DWITH_BDB=ON -DWITH_ZMQ=ON -DBUILD_BENCH=ON -DBUILD_FUZZ_BINARY=ON -DWERROR=ON
 
       - name: Save vcpkg binary cache
         uses: actions/cache/save@v4