Fixed UPGRADE-3.0.md markup
minor #12215 Fixed UPGRADE-3.0.md markup (lyrixx)

This PR was merged into the 2.5 branch.

Discussion
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Fixed UPGRADE-3.0.md markup

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
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eb5f60c Fixed UPGRADE-3.0.md markup