Use the defined strong colour instead of using the default

[green7ea]

In theme definitions, a colour was assigned to strong as seen bellow

(setq nano-color-critical   "#EBCB8B") ;; Aurora / nord 11

Unfortunately, strong didn't use this defined colour but the default instead

:foreground (face-foreground 'nano-face-default)

This commit fixes that by using the strong colour that is defined in themes.

[green7ea]

I noticed this when setting strong to another colour in a custom theme and the function names were the same colour as the normal text. With this change, a custom theme, that overwrites strong has a different function name colour as seen bellow.

[rougier]

Thanks for the report and the fix!