chore: SASS clean up

demo/src/sass/components/buttons.scss

@@ -45,7 +45,7 @@
   }
 
   &.tab-focus {
-    @include tab-focus();
+    @include tab-focus;
   }
 
   &:active {
@@ -64,7 +64,7 @@
 
 // Count bubble
 .button__count {
-  animation: fadein 0.2s ease;
+  animation: fade-in 0.2s ease;
   background: $color-button-count-background;
   color: $color-button-count-text;
   margin-left: ($spacing-base * 0.75);

demo/src/sass/components/header.scss

@@ -7,7 +7,7 @@ header {
   text-align: center;
 
   h1 span {
-    animation: shrinkHide 1s cubic-bezier(0.175, 0.885, 0.32, 1.275) 2s forwards;
+    animation: shrink-hide 1s cubic-bezier(0.175, 0.885, 0.32, 1.275) 2s forwards;
     display: inline-block;
     font-weight: $font-weight-light;
     opacity: 0.5;

demo/src/sass/components/links.scss

@@ -5,7 +5,7 @@
 // Make a <button> look like an <a>
 button.faux-link {
   @extend a; // stylelint-disable-line
-  @include cancel-button-styles();
+  @include cancel-button-styles;
 }
 
 // Links
@@ -39,7 +39,7 @@ a {
   }
 
   &.tab-focus {
-    @include tab-focus();
+    @include tab-focus;
   }
 
   &.no-border::after {