framework: Don't enable VK_LUNARG_direct_driver_loading
Current code enables all available instance extensions, however this one generates a warning from the loader when enabled but not actually used:
The VK_LUNARG_direct_driver_loading extension was enabled but
the pNext chain of VkInstanceCreateInfo did not contain the
VkDirectDriverLoadingListLUNARG structure.
Don't enable it to avoid the noise in the test results.