Fix broken doc formatting by adding missing blank line

[AdeelH]

What does this PR do?

This PR fixes currently broken (see screenshot below) formatting of the "Examples" section of pl_bolts.models.self_supervised.Moco_v2's docstring.

Before submitting

• [ ] Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• [ ] Did you make sure to update the documentation with your changes?
• [ ] Did you write any new necessary tests? [not needed for typos/docs]
• Did you verify new and existing tests pass locally with your changes?
• [ ] If you made a notable change (that affects users), did you update the CHANGELOG?

PR review

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Anyone in the community is free to review the PR once the tests have passed.
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[otaj]

Thank you!