Remove mention of devel branch from tutorial

[kprosise]

A mention of 'platform-devel' found in the 'customizing the platform' tutorial was replaced with 'platform-main'.

Grep'd all the tutorial for any other mentions where not appropriate.

No QA steps performed.

No issues to link, minor fix.

Readiness

• Merge (pending reviews)
• Merge after date or event
• Draft

Overview

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Checklist

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• Run spelling and grammar check, preferably with linter.
• Avoid changing any header associated with a link/reference.
• Step through instructions (or ask someone to do so).
• Review for wordiness
• Match tone and style of page/section.
• Run make linkcheck.
• View HTML in a browser to check rendering.
• Use semantic newlines.
• follow best practices for commits.
  • Descriptive title written in the imperative.
  • Include brief overview of QA steps taken.
  • Mention any related issues numbers.
  • End message with sign off/DCO line (-s, --signoff).
  • Sign commit with your gpg key (-S, --gpg-sign).
  • Squash commits if needed.
• Request PR review by a technical writer and at least one peer.

Comments

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[doanac]

Docs for 1eaef53 are browsable at: https://ci.foundries.io/projects/fio-docs/builds/2483/docs/artifacts/html/index.html