This patch makes us commit to the deemphasized color descriptive pattern throughout settings.
I also made some changes where some settings were using description and should most likely be using a label instead and vice versa.
Quick note that if the descriptive text is tied to an input such as a checkbox or toggle, as opposed to a section heading, we opt for the `.text-deemphasized` class/treatment where not only do we use the `--text-color-deemphasized` color but also shrink the font size. You'll see I opted for such treatment in the Experiments page checkbox list.
Differential Revision: https://phabricator.services.mozilla.com/D197615
48386fea6c