updating tests for Reverse-String exercise

[jagdish-15]

Pull Request: Update Test Suite for Reverse-String Exercise

This pull request updates the test suite for the Reverse-String exercise, bringing it in line with the latest problem specification. With this update, all tests for the exercise are now fully synchronized.

[siebenschlaefer]

Did you write an example solution in C that deals with unicode and grapheme clusters?
Do we really expect our students to do that?

[wolf99]

The current tests and example implementation do not handle wide characters, grapheme clusters, UTF, etc. It only handles 8-bit ASCII characters.

So unless this exercise is radically changed then these tests should be marked as not implemented and the failing tests removed.

It mat be a good addition to the track to have an exercise that handles such characters (I don't think we have any other such exercise). But I don't know if this should be that exercise, and I don't think such a change is within the scope of the simple update that was intended.