Change maximum smoothing factor from 1 to 0.999. (#1974)

1 as a smoothing factor always leads to a constant value of 0 being plotted.
0.999 is the actual highest value you can select for meaningful smoothing.

Author: flostim

tensorboard/plugins/scalar/tf_scalar_dashboard/tf-scalar-dashboard.html

@@ -84,7 +84,7 @@
             weight="{{_smoothingWeight}}"
             step="0.001"
             min="0"
-            max="1"
+            max="0.999"
           ></tf-smoothing-input>
         </div>
         <div class="sidebar-section">