fix(lib): meaningless use(Buefy) (#257)

Fixes the issue that `use(Buefy)` in the root index file was
meaningless or rather harmful to Vue 3 apps. It caused a "not a
function" error in some environment:
see #221 (comment)
Simply removes `use(Buefy)` in the root index file.

packages/buefy-next/src/index.js

@@ -2,7 +2,7 @@ import * as components from './components'
 
 import { merge } from './utils/helpers'
 import config, { setOptions, setVueInstance } from './utils/config'
-import { use, registerComponentProgrammatic } from './utils/plugins'
+import { registerComponentProgrammatic } from './utils/plugins'
 
 import ConfigComponent from './utils/ConfigComponent'
 
@@ -22,8 +22,6 @@ const Buefy = {
     }
 }
 
-use(Buefy)
-
 export default Buefy
 
 // export all components as vue plugin