Get rid of --text-primary-color which is deprecated

[mercmobily]

In this file you are still using --text-primary-color:

paper-fab/paper-fab.html

Line 68 in 8dcf4f1

color: var(--text-primary-color);

This stile is now deprecated:

https://github.com/PolymerElements/paper-styles/blob/master/default-theme.html#L64-L68

[keanulee]

Should replace it with --dark-theme-text-color to keep the default value consistent. This would be breaking API change for paper-fab though (since --text-primary-color will be no longer available), so best to leave it until the next breaking release.

[mercmobily]

I frankly think that using --dark-theme-text-color has the potential of not being so good, since it feels to me like it's only a variable meant to facilitate the setting of the "real" paper variables ( --primary-color --light-primary-color, --dark-primary-color, etc). The only other element using a --dark-theme variable is the paper-toolbar.
In my own CSS I don't even set the --dark-theme or light-theme variables.