Mirror Freeform's BACK icon for RTL languages

When the system language is set to Right-to-Left languages
(e.g., Arabic), the back arrow appears in the wrong direction.

To resolve this issue, set "android:autoMirrored" to true
in the vector file.

Bug: 360764398
Test: manual UI check

Change-Id: I4296c331e3957e8196c3bb6f575ed4e53fa6af99