add !default in marketing/support/variables; plan removal of unused marketing vars

Author: shawnbot

src/marketing/support/variables.scss

@@ -24,11 +24,11 @@ $h000-size: 64px !default;
 $h000-size-mobile: 48px !default;
 
 // Colors
-$green-mktg: mix($green-500, $green-400, 50%);
-$blue-mktg: mix($blue-400, $blue-500, 42%);
+$green-mktg: mix($green-500, $green-400, 50%) !default;
+$blue-mktg: mix($blue-400, $blue-500, 42%) !default;
 
 // Animations
-$transition-time: 0.4s;
+$transition-time: 0.4s !default;
 
 // Increases primer-core scale first by 8px for spacer-7 then by 16px step increments for spacer-8 to spacer-12
 // i.e. After 40px, we have 48, 64, 80, 96, etc.
@@ -39,8 +39,10 @@ $spacer-10: $spacer * 12 !default; // 96px
 $spacer-11: $spacer * 14 !default; // 112px
 $spacer-12: $spacer * 16 !default; // 128px
 
-$marketingSpacers: $spacer-7, $spacer-8, $spacer-9, $spacer-10, $spacer-11, $spacer-12;
-$allSpacers: $spacer-1, $spacer-2, $spacer-3, $spacer-4, $spacer-5, $spacer-6, $spacer-7, $spacer-8, $spacer-9, $spacer-10, $spacer-11, $spacer-12;
+// TODO@14.0.0: remove $marketingSpacers (unused)
+$marketingSpacers: $spacer-7, $spacer-8, $spacer-9, $spacer-10, $spacer-11, $spacer-12 !default;
+// TODO@14.0.0: remove $allSpacers (unused)
+$allSpacers: $spacer-1, $spacer-2, $spacer-3, $spacer-4, $spacer-5, $spacer-6, $spacer-7, $spacer-8, $spacer-9, $spacer-10, $spacer-11, $spacer-12 !default;
 
 $marketing-spacers: (
   7: $spacer-7,