Increase vtable size for String class

Tracks libcore change 5458546631c65f6d375b6a1780d36d0abb5b95af which
increases vtable size for String by four.

Bug: 28108421
Change-Id: I3f7b373ffc08a0f5351f04b5045866ea040f8e6e
(cherry picked from commit 478078a8f9375ec53a3c77c19c0cdb82a9917c88)
1 file changed