Update pr_validation.yml

Author: ccassise

.github/workflows/pr_validation.yml

@@ -124,7 +124,7 @@ jobs:
       shell: pwsh
       run: |
         git clone https://github.com/microsoft/vcpkg.git
-        cmd.exe \c '.\vcpkg\bootstrap-vcpkg.bat'
+        .\vcpkg\bootstrap-vcpkg.bat
 
     - name: Configure CMake
       run: >