Allow Zoekt in Search API for blobs scope when Elasticsearch disabled

What does this MR do and why?

• Before, we were checking for use_elasticsearch? only. Zoekt was not getting considered, and it was returned as bad_request. Updated the logic to use search_type that considers zoekt also.

• Some Rubocop fixes

References

#572479 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Disable Advanced search from Application settings and keep Zoekt search enabled.
• Send an API request like this: https://gdk.test:3443/api/v4/groups/24/search?scope=blobs&search=test&search_type=zoekt.
• On master it was error which is wrong.
• On the MR branch, it is returning results.

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