Merge "Remove required field from libtextclassifier." into rvc-dev am: 3e21ecdf3b am: c15a185f15 am: d387cdff35

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libtextclassifier/+/10634121

Change-Id: I8acd5f1177208fd7b6d5a1012bcb542567edc66f