docs: update workato docs (#2353)

## Summary

- Remove OAuth 2.0 authentication flow, keeping only API token
authentication as a single streamlined set of steps.
- Add a lead paragraph and horizontal rule at the top of the page for
consistency with other integration pages.
- Update connector details to reflect current behavior: crawler type
list (removed JSDOM), memory range info, validation rules for URL fields
and dataset item limits, Actor name format (`owner/name` with slash and
tilde).
- Remove promotional/filler language and fix formatting to match Apify
docs style guide: remove italics from action/trigger descriptions, use
bold with dashes for definition lists, add periods to full-sentence list
items, fix heading hierarchy, and shorten front matter description to
meet the 140-160 character SEO limit.
- Fix markdownlint errors (indented sub-list, missing blank lines).
- Update the Discord link text to "developer community on Discord" and
replace the removed OAuth troubleshooting tip with a validation errors
tip.
- Delete unused OAuth-related screenshots.

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Co-authored-by: Marcel Rebro <marcel.rebro@apify.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people