Utilization of six library have been removed since
Ic6da328a6219c8a00d38602f6b539a2ff5be1b2e .
However an import statement for six in tools/pyir.py
has not been removed.
So remove the import statement for six in tools/pyir.py.
Signed-off-by: Takashi Natsume <takanattie@gmail.com>
Change-Id: Iff0252ab07cef36b0ec8f4abcc3092959fae161c