updated nccl postinstall for pcluster v 3.13 and above

[nghtm]

Issue #, if available:

Description of changes: Remove OFI-NCCL installation as this is precompiled with EFA installer, update NCCL to latest compatible version of OFI-NCCL installed in pcluster AMI as of 09/03/2025 (https://github.com/aws/aws-ofi-nccl/releases/tag/v1.14.2).

This reference branch will be used for AI/ML Pcluster workshop that specifies use of pcluster 3.13, and does not require install of OFI NCCL.

https://catalog.workshops.aws/ml-on-aws-parallelcluster/en-US/03-cluster/02-setup-cluster

$ dpkg -l | grep nccl
ii  libnccl-ofi:amd64                          1.14.2-1                                amd64        NCCL libfabric plugin
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confirming successful NCCL tests on AMI and with Container using these post-install scripts.

test on 2x g5.8xlarge (4x a10 per node) below: nccl-all-reduce-val.log

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[nghtm]

Unable to create fork on /aws-samples due to permissions error

git push upstream ref/workshop

remote: Permission to aws-samples/aws-parallelcluster-post-install-scripts.git denied to nghtm.
fatal: unable to access 'https://github.com/aws-samples/aws-parallelcluster-post-install-scripts.git/': The requested URL returned error: 403