refactor(Accordion): merge accordion selectors for border-radius rule

Author: mrholek

scss/_accordion.scss

@@ -134,17 +134,12 @@
     &:last-child { border-bottom: 0; }
 
     // stylelint-disable selector-max-class
-    > .accordion-header .accordion-button {
-      &,
-      &.collapsed {
-        @include border-radius(0);
-      }
-    }
-    // stylelint-enable selector-max-class
-
-    > .accordion-collapse {
+    > .accordion-collapse,
+    > .accordion-header .accordion-button,
+    > .accordion-header .accordion-button.collapsed {
       @include border-radius(0);
     }
+    // stylelint-enable selector-max-class
   }
 }