Fix some grammar issues

[mboersma]

Replaces "till" with "until" and inserts the required hyphen into the phrase "long-running."

[azuresdkci]

View a preview at https://prompt.ws/r/Azure/azure-cli/5081
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[sptramer]

Docs 👍 LGTM

[mboersma]

Some linting error seems to have crept into the KnackConversion branch, so I fixed it in 6c0c0ce.

[derekbekoe]

@mboersma yes pylint released an update that added some new rules today... Glad it was easy to fix.

[azuresdkci]

View a preview at https://prompt.ws/r/Azure/azure-cli/5081
This is an experimental preview for @microsoft.com users.
(It may take a minute or two for your instance to be ready)
Email feedback to 'azfeedback' with subject 'Prompt Feedback'.

[derekbekoe]

Running CI again to verify no bad git merge.
The pylint fix you made was already merged in by another PR.
Once CI is green, I'll merge.