fix(vite): Ensure sentryVitePlugin always returns an array of plugins

[nicohrubec]

sentryVitePlugin is typed to return VitePlugin[]. The problem is that in case the factory we use returns an array with only a single entry, unplugin will return a single plugin instead of an array. This can happen when the factory bails early and returns only the sentry-noop-plugin.

In other plugins this doesn't seem to be an issue, since we use any as the return type there.