Bump manifest version up from 1 to 2

ApiBase#dieWithError used by ApiWikispeech require MediaWiki 1.29,
i.e. no longer compatible with manifest version 1.

As this allows for descriptions of configuration values,
this might do it for T167300.

Bug: T243376
Change-Id: Idcd73cb390d074acd315f684cf0315e88e4644b2