Remove black color from Rascal prompt

[linuswagner]

Fixes #1806

By removing the color from the prompt, making it only bold, the shell can decide about coloring, which should allow the prompt to be always readable

[linuswagner]

Likely fails, because it works on top of the current head of the repo (d962e8e) which also fails tests

[jurgenvinju]

Thanks @linuswagner ; we'll see if the tests run now due to the fixes on the main branch.

[DavyLandman]

It's not actually black, it's the ANSI color code for black, that a theme redefines for what it means on this specific terminal. Like dark themes and light themes map that same color code to a different color.

Could you run some tests on different themes to see how it behaves?

[DavyLandman]

Here is one to test out:

echo -e "\033[30;1m rascal>"

And testing it, depending on your color scheme, it's indeed hard to read. It might mean that the person who wrote the prompt codes, was working on a terminal with a light color scheme.

So yes, I think this is the right fix 👍