docs: api: amend changelog for API 1.28 for "force" option

This option was added in 8cb2229cd18c53bdbf36301f26db565a50027d6a for
API version 1.28, but forgot to update the documentation and version
history.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/api/version-history.md

@@ -487,6 +487,7 @@ keywords: "API, Docker, rcli, REST, documentation"
 * `POST /services/create` and `POST /services/(id or name)/update` now accept an optional `RollbackConfig` object which specifies rollback options.
 * `GET /services` now supports a `mode` filter to filter services based on the service mode (either `global` or `replicated`).
 * `POST /containers/(name)/update` now supports updating `NanoCpus` that represents CPU quota in units of 10<sup>-9</sup> CPUs.
+* `POST /plugins/{name}/disable` now accepts a `force` query-parameter to disable a plugin even if still in use.
 
 ## v1.27 API changes