[LLDB][Python] warning fix for LLDBSwigPythonBreakpointCallbackFunction

[LLDB][Python] warning fix for LLDBSwigPythonBreakpointCallbackFunction

This is a quick followup to this commit:

https://reviews.llvm.org/rGa69bbe02a2352271e8b14542073f177e24c499c1

In that, I #pragma-squelch this warning in `ScriptInterpreterPython.cpp`
but we get the same warning in `PythonTestSuite.cpp`.

This patch squelches the same warning in the same way as the
reviweed commit.   I'm submitting it without review under the
"obviously correct" rule.

At least if this is incorrect the main commit was also incorrect.

By the way, as far as I can tell, these functions are extern "C" because
SWIG does that to everything, not because they particularly need to be.