Fixed duplicate/double "which" in leading paragraph

[samsmithnz]

Why:

Fixes typo in leading paragraph. #16056

What's being changed:

from:

You can also use the security overview to see which which security features are enabled for your repositories and to configure any available security features that are not currently in use.

to:

You can also use the security overview to see which security features are enabled for your repositories and to configure any available security features that are not currently in use.

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• I have reviewed my changes in staging (look for "Automatically generated comment" and click Modified to view your latest changes).
• For content changes, I have completed the self-review checklist.

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Content directory changes

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Source	Preview	Production	What Changed
content/code-security/security-overview/about-the-security-overview.md	Modified	Original

[ramyaparimi]

@samsmithnz
Thanks so much for opening a PR with this fix! I'll get this merged once tests are passing 🍏

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