Remove unnecessary legacy CSS properties

We depend un such modern things anyway, having these kinds of properties
are more confusing than helpful. Let's not give the impression that we
make any attempt to work in old browsers.

app/styles/input.css

@@ -25,8 +25,7 @@ input[type=url],
 input[type=week],
 textarea {
   /* Disable default rendering */
-  -webkit-appearance: none;
-  -moz-appearance: none;
+  appearance: none;
   background: none;
 
   padding: 5px;
@@ -43,8 +42,7 @@ input[type=submit],
 button,
 select {
   /* Disable default rendering */
-  -webkit-appearance: none;
-  -moz-appearance: none;
+  appearance: none;
   background: none;
 
   padding: 5px;
@@ -97,14 +95,6 @@ textarea:focus {
   outline: none;
 }
 
-input[type=button]::-moz-focus-inner,
-input[type=color]::-moz-focus-inner,
-input[type=reset]::-moz-focus-inner,
-input[type=submit]::-moz-focus-inner,
-button::-moz-focus-inner {
-  border: none;
-}
-
 input:not([type]):disabled,
 input[type=button]:disabled,
 input[type=color]:disabled,