Resistor color exercise description doesn't match its instructions.md file

[mkushnikov]

Currently, the instruction file contains a clear description of what the student has to do(The goal of this exercise at the bottom).

But this paragraph is missing from the exercise description on the website.

As for me personally, it was unclear until I'd checked the test cases.

[ErikSchierboom]

Ah, that must be because we only update the READMEs from time to time. With v3, we'll do this more regularly. If you check https://github.com/exercism/csharp/blob/main/exercises/practice/resistor-color/.docs/instructions.md, you'll see that it contains the latest version of the description, which means that the text will be updated when v3 launches. We can't update the v2 contents anymore, so we have to wait for v3.