docs: Update ambient mode to mention disabling bitmap filtering

<ul>

<li>For devices that use low-bit ambient mode, the screen supports fewer bits for each color

in ambient mode, so you should disable anti-aliasing.</li>

in ambient mode, so you should disable anti-aliasing and bitmap filtering when the device switches

to ambient mode.</li>

<li>For devices that require burn-in protection, avoid using large blocks of white pixels in

ambient mode and do not place content within 10 pixels of the edge of the screen, since the

system shifts the content periodically to avoid pixel burn-in.</li>

<p>For more information about low-bit ambient mode and burn-in protection, see

<a href="{@docRoot}design/wear/watchfaces.html#SpecialScreens">Optimize for Special

Screens</a>.</p>

Screens</a>. For more information on how to disable bitmap filtering, see

<a href="{@docRoot}training/wearables/watch-faces/performance.html#BitmapFiltering">Bitmap

Filtering</a>.</p>

<h2 id="Modes">Respond to Changes Between Modes</h2>

setFilterBitmap()} method. <a href="#fig2">Figure 2</a> shows a magnified view of a clock hand with

and without bitmap filtering.</p>

<p class="note"><strong>Note:</strong> In low-bit ambient mode, the system does not reliably

render the colors in the image for bitmap filtering to process successfully. When ambient mode is

active, disable bitmap filtering.</p>

<h2 id="OutDrawing">Move Expensive Operations Outside the Drawing Method</h2>