Fix conflicting Dependabot security update PR limit (10, not unlimited)

[Himanshucodess]

Summary

• The 'open-pull-requests-limit' section of the Dependabot options reference claimed 'There is no limit on the number of open pull requests for security updates.'
• That contradicts the Dependabot errors troubleshooting page ('Pull request limit reached'), which documents a limit of 10 open security update PRs and 5 (configurable via 'open-pull-requests-limit') version update PRs, with separate limits so version PRs cannot block security PRs.
• Verified behavior: security update PR limit = 10 (not configurable via 'open-pull-requests-limit'); version update PR limit = 5 by default (configurable). This matches the troubleshooting page, the live docs, and community/secondary confirmation of a separate non-configurable internal limit of 10 for security updates.
• Corrected the note in 'content/code-security/reference/supply-chain-security/dependabot-options-reference.md' to state the 10-PR security update limit, which is not configurable using 'open-pull-requests-limit'. No other occurrences of the incorrect 'no limit' claim were found repo-wide.

Validation

• Ran: 'git diff --check' (clean), 'git status'/'git diff' review (single intended line changed), repo-wide 'git grep' for the incorrect sentence (no remaining occurrences) and for related limit statements (only the correct troubleshooting page entry remains).
• Manually inspected Markdown syntax, front matter (untouched), links/anchors (untouched), and surrounding terminology (consistent).
• NOT run: full npm lint/test suite (requires heavy install; impractical for a one-line docs change — CI on the PR will cover it).

Closes #46116

[github-actions]

How to review these changes 👓

Thank you for your contribution. To review these changes, choose one of the following options:

• Spin up a codespace
• Set up a local development environment

A Hubber will need to deploy your changes internally to review.

Table of review links

Note: Please update the URL for your staging server or codespace.

The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
code-security/reference/supply-chain-security/dependabot-options-reference.md	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

🤖 This comment is automatically generated.

[subatoi]

This isn't open to contributors yet, so I'm going to close this out. Until an issue has help wanted attached, we haven't had time to do a proper assessment and we don't know whether it's something we need to fix internally, or how many articles are affected and what the scope of the fix will be. Sorry this won't have been the outcome you were hoping for.