[Documentation] Fix typos

[vipocenka]

This PR fixes minor typos and improves wording in the following files:

• .github/ISSUE_TEMPLATE/feature_request.md:
  Corrected a typo in the "about" field of the feature request template.

• docs/source/development-guide/workers/insight_worker.rst:
  Fixed typos and improved the readability of certain sentences in the insight worker documentation.

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Notes for Reviewers

Please review the changes to ensure no semantic meaning was altered during the corrections.

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Signed Commits

• Yes, I signed my commits.

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Changes

feature_request.md

• Corrected "an feature" to "a feature" in the "about" field for grammatical correctness.

insight_worker.rst

• Fixed "double checking" to "double-checking."
• Improved sentence structure for clarity and consistency.