Remove unused this in method unwind callback

This object isn't used in any of the receivers and it is not easy to get
this for quick frames without instrumentation stack. When there is a
real need we can implement a way to get this object.

Bug: 206029744
Test: art/test.py
Change-Id: I2c74920ee37cc787978c7ce759cf1be5f6b15e6d
10 files changed