Switch to using gray icon for Bluetooth imaging devices

All the other Bluetooth icons were switched to gray at some point in the
past, but we must have missed this one.

Bug: 63858978
Test: make RunSettingsRoboTests
Change-Id: I2ebefa42f3ecff8ae6d58f4bdb22dce39ae4dbd4

tests/robotests/src/com/android/settings/bluetooth/BluetoothDevicePreferenceTest.java

@@ -15,6 +15,7 @@
  */
 package com.android.settings.bluetooth;
 
+import android.bluetooth.BluetoothClass;
 import android.bluetooth.BluetoothDevice;
 import android.content.Context;
 import android.os.UserManager;
@@ -136,4 +137,13 @@ public class BluetoothDevicePreferenceTest {
 
         assertThat(mPreference.shouldHideSecondTarget()).isFalse();
     }
+
+    @Test
+    public void imagingDeviceIcon_isICSettingsPrint() {
+        when(mCachedBluetoothDevice.getBtClass()).thenReturn(
+                new BluetoothClass(BluetoothClass.Device.Major.IMAGING));
+        mPreference.onDeviceAttributesChanged();
+        assertThat(mPreference.getIcon()).isEqualTo(
+                mContext.getDrawable(R.drawable.ic_settings_print));
+    }
 }