Fix install link in Elasticsearch integraton docs

What does this MR do?

Elasticsearch Integration page > Installing Elasticsearch (Frontend - File-view) contains broken link to ES installation instructions

You can follow the steps as described in the official web site or use the packages that are available for your OS.

Current link leads to 404 Page not found

MR changes link to match the updated installation instructions URL

What are the relevant issue numbers?

Fixes #10739 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer