Replace `MeiliSearch` occurrences with `Meilisearch` in the code

[Clémentine]

I see some naming used in the code base using MeiliSearch, like isMeiliSearchRunning. Since it's in the code, I did not want to take the risk to change it here #229

Maybe you don't want to change it at the end @mdubus, but I open this issue to let you know :)