gdb/testsuite: remove unused "global" statements in Python files Fix the flake8 warnings of this type: gdb/testsuite/gdb.python/py-disasm.py:855:9: F824 `global current_pc` is unused: name is never assigned in scope Change-Id: If492c69553cebea932cfb21e6fea26529761254c Approved-By: Tom Tromey <tom@tromey.com>