Syntax fix

Author: walbourn

build/DirectXTex-GitHub-CMake-Dev17.yml

@@ -62,7 +62,7 @@ variables:
   Codeql.Enabled: false
   VCPKG_ROOT: $(Build.SourcesDirectory)/vcpkg
   VCPKG_CMAKE_DIR: $(Build.SourcesDirectory)/vcpkg/scripts/buildsystems/vcpkg.cmake
-  VCPKG_MANIFEST_DIR: '$(Build.SourcesDirectory)/build
+  VCPKG_MANIFEST_DIR: $(Build.SourcesDirectory)/build
   VS_GENERATOR: 'Visual Studio 17 2022'
   WIN10_SDK: '10.0.19041.0'
   WIN11_SDK: '10.0.22000.0'