Include ".active" navbar breaking change in v5 migration docs

Created by: jhthompson

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

• Add description of a navbar breaking change to the v5.0 migration documentation navbar section
  • Change: https://github.com/twbs/bootstrap/pull/32730
  • I am willing to open a PR to fix, but could not find source file to edit (is there a v5.0 branch to make the PR against?)

Motivation and context

Navbar breaking change¹ was not listed in the v5 migration docs under the navbar section. It would nice to have it listed for easier migration as I almost missed this breaking change. Other related doc fixes²³

1. https://github.com/twbs/bootstrap/pull/32730 ↩

2. https://github.com/twbs/bootstrap/pull/32589 ↩

3. https://github.com/twbs/bootstrap/issues/32583 ↩