Clean up launched VDM custom IME flag

Launched in Android 15.

No CTS logic was ever based on the flag being off, so no
need to CP this.

#codehealth

Bug: 292214444
Bug: 379646558
Test: presubmit
Flag: EXEMPT cleanup
Change-Id: I7b43b8b3cbb6d2df94db9bf2b589bad35661b696