Fix divider color on navigation drawer and steppers (#4716)

* fix(divider): fix stepper divider color

* fix(divider): fix navigation drawer divider color

Author: peluprvi

src/stylus/components/_navigation-drawer.styl

@@ -9,7 +9,7 @@ v-navigation-drawer($material)
       background-color: $material.dividers
 
   .v-divider
-    background-color: $material.dividers
+    border-color: $material.dividers
 
 theme(v-navigation-drawer, "v-navigation-drawer")
 

src/stylus/components/_steppers.styl

@@ -17,7 +17,7 @@ v-stepper($material)
 
   .v-stepper__header
     .v-divider
-      background: rgba($material.fg-color, $material.divider-percent)
+      border-color: rgba($material.fg-color, $material.divider-percent)
 
   .v-stepper__step
     &--active