[GraphBolt][CUDA] refine the node_classification examples.

[mfbalin]

Description

Fixing minor typos and aligning the multiGPU example with the tutorial updated in #7126.

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature]])
• I've leverage the tools to beautify the python and c++ code.
• The PR is complete and small, read the Google eng practice (CL equals to PR) to understand more about small PR. In DGL, we consider PRs with less than 200 lines of core code change are small (example, test and documentation could be exempted).
• All changes have test coverage
• Code is well-documented
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change
• Related issue is referred in this PR
• If the PR is for a new model/paper, I've updated the example index here.

Changes

[dgl-bot]

To trigger regression tests:

• @dgl-bot run [instance-type] [which tests] [compare-with-branch];
  For example: @dgl-bot run g4dn.4xlarge all dmlc/master or @dgl-bot run c5.9xlarge kernel,api dmlc/master

[mfbalin]

@TristonC you can run the papers100M with the updated multiGPU script in this PR.

[dgl-bot]

Commit ID: 12ad220989afe68dc45fe27a263d675223af3456

Build ID: 1

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: e90373d493d347d4add15dcd43477e84aa87a316

Build ID: 2

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: 6bbe6cb38f1d4f2a68a5abd7c038ad43c050817c

Build ID: 3

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: f6308dddcbafb6326c50c3a167c4d02c6b66cd20

Build ID: 4

Status: ⚪️ CI test cancelled due to overrun.

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[dgl-bot]

Commit ID: 2bbc93d3458112f1d52f078bd663f37706c43cdb

Build ID: 5

Status: ✅ CI test succeeded.

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[frozenbugs]

LGTM @RamonZhou please take a second look and approve.

[RamonZhou]

LGTM