AOSP/Gallery2 - Update language to comply with Android's inclusive language guidance.

See https://source.android.com/setup/contribute/respectful-code for reference

BUG=161896447

Test: Manual.

$ ls -l out/target/product/bonito/product/app/Gallery2/Gallery2.apk
  -rw-r----- 1 rtenneti primarygroup 7429083 Jul 28 21:40 out/target/product/bonito/product/app/Gallery2/Gallery2.apk

$ adb install -r out/target/product/bonito/product/app/Gallery2/Gallery2.apk

Change-Id: Ife78a86551991069f203ec138f46b222973519cc