fix(tabs): Remove tab animation on active tab (#3658)

* fix(tabs): Remove tab animation on active tab

* fix(tabs): Remove ref to keyframes

Author: brandonferrua

RELEASENOTES.md

@@ -4,6 +4,10 @@
 ## Release 2.8.3 - February 4, 2019
 
 ## Components
+### [Tabs](https://www.lightningdesignsystem.com/components/tabs)
+#### Changed
+- Removed animation when invoking an active tab
+
 ### [Global Navigation](https://www.lightningdesignsystem.com/components/global-navigation)
 #### Fixed
 - Fixed issue where a navigation item would lose its background color when active and/or hovered.

ui/components/tabs/RELEASENOTES.md

@@ -3,6 +3,12 @@
 # Tabs Release Notes
 
 <!-- ## [Unreleased] -->
+## 2.8.3
+
+### Changed
+
+- Removed animation when invoking an active tab
+
 ## 2.8.0
 
 ### Added

ui/components/tabs/base/_index.scss

@@ -3,22 +3,6 @@
 
 @import 'deprecate';
 
-// Animation for `slds-is-active` state
-@keyframes shadow {
-
-  0% {
-    box-shadow: inset 0 0 $brand-light;
-  }
-
-  50% {
-    box-shadow: inset 0 rem(-30px) $brand-primary-transparent-40;
-  }
-
-  100% {
-    box-shadow: inset 0 rem(-40px) $brand-light;
-  }
-}
-
 /**
  * @summary Initializes a default tablist
  *
@@ -88,7 +72,6 @@
   &.slds-active,
   &.slds-is-active {
     color: $color-text-action-label-active;
-    animation: shadow 300ms;
 
     &:after {
       background-color: $brand-primary;