Let's try keeping labels the current color, period

... and we'll see how that goes.  (Had dark label, with the color set somewhere deep
in Bulma i think, on a dark blue background, and that didn't work out so well
contrast-wise.)

agaric/sass/agaric/_base.form.scss

@@ -4,11 +4,11 @@
 //
 // Styleguide: Base.Form
 
+.label {
+  color: currentColor;
+}
+
 .is-dark {
-  .field {}
-  .label {
-    color: currentColor;
-  }
   .select {
     select {
       border-color: $dark;