[UPGRADE-2.2.md] add information about route pattern => path renaming

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This updates the UPDGRADE-2.2.md with missing information.