refactor: 3 small changes in semantic colors

[lauthieb]

There are some changes in semantic colors for 3 colors:

backgroundPrimary => from grey800 to grey900
backgroundSecondary => from grey900 to black
backgroundTertiary=> from black to grey800

To help you, here is the PR on vitamin-web: Decathlon/vitamin-web#1127

Thanks for your understanding.

[baptistedajon]

Already done in PR ☝

[lauthieb]

thanks @baptistedajon :)