Trim UpdateDevice exception message to a simple statement

Exception messages should describe what went wrong; how to recover belongs in
the API doc-comment (which Device.h already has). Aligns with the simple-
statement style of the other DeviceImpl exception messages.

[Created by Copilot on behalf of @bghgary]

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: bghgary

Core/Graphics/Source/DeviceImpl.cpp

@@ -110,7 +110,7 @@ namespace Babylon::Graphics
         std::scoped_lock lock{m_state.Mutex};
         if (m_state.Bgfx.Initialized)
         {
-            throw std::runtime_error{"UpdateDevice called while rendering is enabled. Call DisableRendering first; the new device will take effect on the next EnableRendering / StartRenderingCurrentFrame."};
+            throw std::runtime_error{"UpdateDevice called while rendering is enabled."};
         }
         m_state.Bgfx.InitState.platformData.context = device;
         m_state.Bgfx.Dirty = true;