Update polaris-tokens/src/token-groups/border.ts

Co-authored-by: Aaron Casanova <32409546+aaronccasanova@users.noreply.github.com>

Author: kyledurand

polaris-tokens/src/token-groups/border.ts

@@ -12,7 +12,7 @@ export type BorderRadiusScale =
 
 export type BorderWidthScale = '1' | '2' | '3' | '4' | '5';
 
-export type BorderExperimentalWidthScale = '0_75' | '1_5';
+type BorderExperimentalWidthScale = '0_75' | '1_5';
 
 export type BorderTokenName =
   | `border-radius-${BorderRadiusScale}`