Make supported bundler version clearer and polish topic
What does this MR do?
Primarily to highlight we want to install a version of bundler lower than v2.
While here, implemented some newer styles and conventions, and gave some sentences an edit.
Related issues
Relates to: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24502.
Author's checklist
Review checklist
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Your team's review (required) -
Technical writer's review (required)
Edited by Evan Read