Improve clarity in upgrade word description in word list docs

What does this MR do?

The description of upgrade word in the Style guide's word list seems to be unclear:

It mentions

Installing a newer major (13.0, 14.0) or minor (13.8, 14.5) version of GitLab.

... however (13.8, 14.5) is not a minor change. It could be confusing because the two numbers suggest an upgrade from one to another. To avoid

Further details

Proposal

To void confusion, it could be better to include just one version in the parenthesis. Like this:

Installing a newer major (13.0) or minor (13.2) version of GitLab.

Related issues

• #388938 (closed)

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
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