Remove unnecessary color declaration

The `color` gets inherited from the `body` and doesn't need to be set.
Furthermore, only setting the colour without also setting
the background colour could cause issues for people
needing to change colour settings.

assets/sass/elements/_tables.scss

@@ -12,7 +12,6 @@ table {
     padding: em(12, 19) em(20, 19) em(9, 19) 0;
 
     text-align: left;
-    color: $black;
     border-bottom: 1px solid $border-colour;
   }