Revert an unnecessary diff vs upstream in Throwables.java.

This diff was one of two restored in http://r.android.com/703085, but
it seems that this one was not required.

Bug: 35910877
Test: `cts-tradefed run cts-dev -m CtsLibcoreTestCases`
Test: Manually check for serialization exceptions on startup via logcat
Change-Id: I00d3f12c244f1e15f51a4ea0b156920f932b2dfe
1 file changed