Add note about rules being enclosed in double quotes

What does this MR do?

Notes in several places that a DAST list of rules to be included or excluded must be enclosed in double quotation marks.

Background information:

DAST allows for specific security checks to be included or excluded by their assigned ID. These IDs are provided in a string, for example, "10045,17742,188292". If the CSV list is not enclosed in double quote marks ("), they are interpreted as numeric values, preventing them from being processed correctly.

This MR was raised responding to a MR discussion thread.

Related issues

N/A

Author's checklist

• Consider taking the GitLab Technical Writing Fundamentals course
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• Ensure that the product tier badge is added to topic's h1.
• Request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are only adding documentation, do not add any of the following labels:

• ~"feature"
• ~"frontend"
• ~"backend"
• ~"bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Review checklist

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• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
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  • Ensure the appropriate labels are added to this MR.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
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• Ensure a release milestone is set.