Remove the extra mapping of field types in ProtoOutputStream

It is very unlikely the protobuf changes the value in descriptor.h,
and if defines an extra mapping, there are several places to maintain:
1. java-stream,
2. cpp-stream,
3. ProtoOutputStream.java
4. ProtoOutputStream.cpp
5. Privacy.h (GetFieldId)
6. StatsLog to generate field id (type << 32 + field number)

Therefore use the current value in descriptor.h seems reasonable unless
they change that, very very unlikely, they probably will just add new
types, and deprect the existing ones like Group.

Test: test output of dumpsys proto
Change-Id: I6e150ab427851dd3b5dd55d3b273deeed7a0963c