docs: Correct documentation to state that NVIDIA container runtime is included, not CUDA toolkit

[bryantbiggs]

Issue number:

Closes #

Description of changes:

• Correct documentation to state that NVIDIA container runtime is included, not the CUDA toolkit
  • The NVIDIA container runtime (usually installed/configured via the NVIDIA *container toolkit) is required on the host when wanting to utilize NVIDIA GPUs within your containers
  • The NVIDIA CUDA toolkit is a user space component for developing CUDA based applications - this not required on the host, nor should it be for containerized environments

XRef - https://github.com/awslabs/amazon-eks-ami/pull/1924#discussion_r1719173076

Testing done: None

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.