Mark encodeSmdxSubjectAndReasonCode incompatibilities

These APIs used to list the runtime exceptions they throw, but don't
anymore. I'm not certain if this is an acceptable API change.

Bug: 154317059
Test: m
Change-Id: I68d28b6091fc293c0e1aa7e2c19d4eb836cc5412
Merged-In: I68d28b6091fc293c0e1aa7e2c19d4eb836cc5412
1 file changed