Bug 896932 - Update assets
Bug 898290 - [Gallery] HD gradient image rename
(cherry picked from commit 7c3603cd825f2312d196f6fe5f9efb83751df261)
Merge pull request #11154 from crh0716/896932

Bug 896932 - Update assets r=stevechung a=hd+
Revert "Merge pull request #11009 from mozshiao9/v1-train_settings_889717"

This reverts commit 7ee822b8ad62cef335c60bda489887353fcd0806, reversing
changes made to 0ce3196d563b07b257850de2583b83f219a98a83.