[v4] [core] Update button borders and background gradient (#5046)

Co-authored-by: Adi Dahiya <adi.dahiya14@gmail.com>

Author: johnly13

packages/core/src/components/button/_common.scss

@@ -48,19 +48,17 @@ $button-box-shadow-overlay-active:
   inset 0 1px 1px rgba($black, 0.1) !default;
 
 $dark-button-box-shadow:
-  0 0 0 $button-border-width rgba($black, 0.4) !default;
+  inset 0 0 0 1px rgba(17, 20, 24, 0.8) !default;
 $dark-button-box-shadow-active:
-  0 0 0 $button-border-width rgba($black, 0.6),
-  inset 0 1px 2px rgba($black, 0.2) !default;
+  inset 0 0 0 1px rgba(17, 20, 24, 0.8) !default;
 $dark-button-intent-box-shadow:
-  0 0 0 $button-border-width rgba($black, 0.4) !default;
+  inset 0 0 0 1px rgba(17, 20, 24, 0.8) !default;
 $dark-button-intent-box-shadow-active:
-  0 0 0 $button-border-width rgba($black, 0.4),
-  inset 0 1px 2px rgba($black, 0.2) !default;
+  inset 0 0 0 1px rgba(17, 20, 24, 0.8) !default;
 
-$button-gradient: linear-gradient(to bottom, rgba($white, 0.8), rgba($white, 0)) !default;
-$button-intent-gradient: linear-gradient(to bottom, rgba($white, 0.1), rgba($white, 0)) !default;
-$dark-button-gradient: linear-gradient(to bottom, rgba($white, 0.05), rgba($white, 0)) !default;
+$button-gradient: linear-gradient(to bottom, rgba($black, 0), rgba($black, 0.05)) !default;
+$button-intent-gradient: linear-gradient(to bottom, rgba($black, 0), rgba($black, 0.05)) !default;
+$dark-button-gradient: linear-gradient(to bottom, rgba($black, 0), rgba($black, 0.05)) !default;
 
 $button-color-disabled: $pt-text-color-disabled !default;
 $button-background-color: $light-gray5 !default;