i18n-calypso: Remove obsolete `componentUpdateHooks`

[componentUpdateHooks](https://github.com/Automattic/wp-calypso/blob/master/packages/i18n-calypso/src/i18n.js#L156) is not being used anywhere in the package besides in the method that pushes items into it - [registerComponentUpdateHook](https://github.com/Automattic/wp-calypso/blob/master/packages/i18n-calypso/src/i18n.js#L418-L420). Therefore, it should be safe to remove it without losing any functionality.

However, since `registerComponentUpdateHook` is being used in a few places in Calypso ([#1](https://github.com/Automattic/wp-calypso/blob/4537033c6794449ce0a10b69d72daf5fa658d553/client/components/community-translator/index.jsx#L41), [#2](https://github.com/Automattic/wp-calypso/blob/31ea12c6617e6298a96402fbc3b0269381de4e8c/client/lib/translator-jumpstart/index.js#L310-L314)), it should be removed from there before removing it from the package.