Remove psr4 autoloading `MeiliSearch` alias

**Description**
Namespace previously was renamed from `MeiliSearch` to `Meilisearch`. In v2 we can remove it.

**Basic example**
```diff
diff --git a/composer.json b/composer.json
@@ -26,7 +26,6 @@
     },
     "autoload": {
         "psr-4": {
-            "MeiliSearch\\": "src/",
             "Meilisearch\\": "src/"
         }
     },
```

**Other**
-
