layers: trivial: remove stray () from end of error message
layers: trivial: remove stray () from end of error message

This wasn't describing a function; the () on the end is just nonsense.

Signed-off-by: Chris Forbes <c3279c50043e18e9442c1ae071cafa0e7a4ca967@google.com>

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools