Minor CSS: make access captcha input like comment box

anonstream/templates/captcha.html

@@ -37,12 +37,13 @@
       border-radius: 2px;
       color: #ddd;
       font-size: 14pt;
-      padding: 4px 5px;
+      padding: 5px 6px;
       width: 10ch;
-    }
-    input[name="answer"]:hover {
-      background-color: #37373a;
       transition: 0.25s;
+    }
+    input[name="answer"]:focus {
+      background-color: black;
+      border-color: #3584e4;
 	}
 	input[type="submit"] {
       font-size: 14pt;