Update tooltip values to meet design specs

app/assets/stylesheets/framework/tooltips.scss

 .tooltip-inner {
-  font-size: $tooltip-font-size;
+  font-size: $gl-font-size-small;
   border-radius: $border-radius-default;
-  line-height: 16px;
+  line-height: $gl-line-height;
   font-weight: $gl-font-weight-normal;
-  padding: 8px;
 }

app/assets/stylesheets/framework/variables_overrides.scss

@@ -48,3 +48,7 @@ $spacers: (
   9: ($spacer * 8)
 );
 $pagination-color: $gl-text-color;
+$tooltip-padding-y: 0.5rem;
+$tooltip-padding-x: 0.75rem;
+$tooltip-arrow-height: 0.5rem;
+$tooltip-arrow-width: 1rem;