Fix incorrect plugin class (spotted by Luis Garrido).

It's SimulatorPlugin, not SimulationPlugin.
(cherry picked from commit d971297ebebd9faf6c2640fdbecdfc553cd8407e)
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f