RFR: 8331018: Clean up non-standard use of /** comments in `jdk.jshell`

[Iris Clark]

On Tue, 23 Apr 2024 23:19:13 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a fix to preempt warnings that would otherwise be introduced by [JDK-8303689](https://bugs.openjdk.org/browse/JDK-8303689), which introduces a new javac lint warning to detect documentation comments in unusual places.
> 
> The comments here are all one-line comments of the form `/***** message ****/`.
> 
> Following the style of an existing similar comment, the comments are changed to the form `//***** message *****`
> That existing comment is in Snippet.java:648
> 
>     //**** internal access ****
>     String name() {
>         return unitName;
>     }

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/18926#pullrequestreview-2018615207