Apply `align-items: center;` to `.input-group` instead of input group sub...

Apply `align-items: center;` to `.input-group` instead of input group sub components, causes `.input-group .form-control` and `.input-group-addon` to be large when next to a tall element

scss/_input-group.scss

@@ -5,6 +5,7 @@
 .input-group {
   position: relative;
   display: flex;
+  align-items: center;
   width: 100%;
 
   .form-control {
@@ -28,10 +29,6 @@
 .input-group-addon,
 .input-group-btn,
 .input-group .form-control {
-  // Vertically centers the content of the addons within the input group
-  display: flex;
-  align-items: center;
-
   &:not(:first-child):not(:last-child) {
     @include border-radius(0);
   }