Clarify the valid update-types values for the ignore block

[yeikel]

Why:

The current example is invalid and causes confusion. A few entries above we list configuration options but are using different values in the examples for the specific entry,

Relevant issue: dependabot/dependabot-core#12953

What's being changed (if available, include any code snippets, screenshots, or gifs):

Updates the valid values for the update-types section of the ignore configuration property for Dependabot

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

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Source	Review	Production	What Changed
code-security/dependabot/working-with-dependabot/dependabot-options-reference.md	fpt ghec ghes@ 3.17 3.16 3.15 3.14	fpt ghec ghes@ 3.17 3.16 3.15 3.14

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[Sharra-writes]

@yeikel Thanks for opening a PR! I'll double check with the Dependabot team and get back to you.

[Sharra-writes]

@yeikel Got confirmation that this change should have been made a while ago and was apparently overlooked, so I'll get this added to the merge queue once checks are passing. Thanks for fixing it!

[github-actions]

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