SI-8215 Removing ASCII art class diagram in Scaladoc for Regex

The Content Hierarchy contains the same information, properly formatted.
See https://groups.google.com/d/msg/scala-language/2T2wKVQiyVg/3-iu19XSTxwJ
SI-8215 Documenting the possibility of IllegalStateExceptions when using MatchIterator

See https://groups.google.com/forum/#!topic/scala-language/2T2wKVQiyVg
Merge pull request #3439 from demobox/issue-8215

SI-8215: Document IllegalStateExceptions thrown by uninitialized MatchIterator from Regex (review by @heathermiller)