GUACAMOLE-152: Fix up new zoom control style.

guacamole/src/main/webapp/app/client/styles/menu.css

@@ -134,8 +134,19 @@
     padding-top: 1em;
 }
 
-.menu-section .zoom-ctrl {
-    width: 4em;
+.menu-section input.zoom-ctrl {
+    width: 2em;
+    font-size: 1em;
+    padding: 0;
+    background: transparent;
+    border-color: rgba(0, 0, 0, 0.125);
+}
+
+.menu-section div.zoom-ctrl {
+    font-size: 1.5em;
+    display: inline;
+    align-content: center;
+    vertical-align: middle;
 }
 
 .menu-section .zoom-ctrl::-webkit-inner-spin-button,