Remove color option in printer profile editor

We don't use it anywhere and its presence keeps confusing users. Kept
in the model since we might want to use it at some later time.

Closes #1790

src/octoprint/templates/snippets/settings/printerprofiles/profileEditorGeneral.jinja2

@@ -19,11 +19,4 @@
             <input type="text" data-bind="value: model">
         </div>
     </div>
-    <div class="control-group">
-        <label class="control-label">{{ _('Color') }}</label>
-        <div class="controls">
-            <select data-bind="value: color, options: availableColors, optionsText: 'name', optionsValue: 'key'">
-            </select>
-        </div>
-    </div>
 </form>