[lldb] Update shebang in heap.py and crashlog.py

lldb/examples/darwin/heap_find/heap.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 #----------------------------------------------------------------------
 # This module is designed to live inside the "lldb" python package

lldb/examples/python/crashlog.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 #----------------------------------------------------------------------
 # Be sure to add the python path that points to the LLDB shared library.