Revert "Add more readable focus state for buttons"

This reverts commit 768cb2a32f2e4c12c823b9da7b7a08e4a70d0922.

CHANGELOG.txt

@@ -42,7 +42,6 @@ Changelog
  * Fix: Rich text processing now preserves non-breaking spaces instead of converting them to normal spaces (Wesley van Lee)
  * Fix: Prevent autocomplete dropdowns from appearing over date choosers on Chrome (Kevin Howbrook)
  * Fix: Prevent crash when logging HTTP errors from Cloudflare (Kevin Howbrook)
- * Fix: Add more readable focus state for admin buttons (Chris Adams)
 
 
 2.4 (19.12.2018)

docs/releases/2.5.rst

@@ -58,7 +58,6 @@ Bug fixes
  * Rich text processing now preserves non-breaking spaces instead of converting them to normal spaces (Wesley van Lee)
  * Prevent autocomplete dropdowns from appearing over date choosers on Chrome (Kevin Howbrook)
  * Prevent crash when logging HTTP errors on Cloudflare cache purging (Kevin Howbrook)
- * Add more readable focus state for admin buttons (Chris Adams)
 
 
 Upgrade considerations

wagtail/admin/static_src/wagtailadmin/scss/components/_forms.scss

@@ -53,7 +53,6 @@ label,
 input,
 textarea,
 select,
-button,
 .halloeditor,
 .tagit {
     appearance: none;
@@ -77,7 +76,6 @@ button,
         background-color: $color-input-focus;
         border-color: $color-input-focus-border;
         outline: none;
-        color: $color-teal-darker;
     }
 
     &:disabled,