Fix: white color headers of hx --health command on light background.

[ghost]

Closes #5516

As said in issue on a light backgrounds white headers (table created with hx --health) are almost invisible. Especially with a light theme on gnome-terminal.

helix/helix-term/src/health.rs

Lines 161 to 164 in b633139

	for heading in headings {
	column(heading, Color::White);
	}
	writeln!(stdout)?;

I thought of 3 possible solutions:

1. Make the color Color::Reset. Then the headings will be the same as the language name color:
   

2. First solution + add dashed line after the headings to make it clearer:
   

3. Use another color from this list:
   
   But in this case, there is also a possibility that the user is using a background with this color.

What would you recommend?