Remove U+1F93B MODERN PENATHLON and U+1F946 RIFLE from emoji

These had remained in Emoji.java although they were removed from Unicode
emoji. The data still needs to be updated to Emoji 5.0, but that will be
done in another CL.

Test: not needed
Bug: 28678294
Change-Id: I491c4bba107b960fb1efccbe19630ab274aa6e29