RFR: JDK-8285869: Selective cleanup in doclint Checker class

[Iris Clark]

On Fri, 29 Apr 2022 00:29:50 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review some localized cleanup for the doclint Checker class, primarily focused on upgrading to the use of "enhanced `switch`"
> 
> The output of one test was changed because of some improvements in one switch statement to eliminate the use of fall-through semantics.

Marked as reviewed by iris (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/8460