Update the installation link

What does this MR do?

The installation link has changed from /installation/ to /install/. This commit will update all the remaining links that are missing.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content