perf scripts python: exported-sql-viewer.py: Change python2 to python

Now that there is also support for python3, there is no need to specify
python2 explicitly.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190412113830.4126-2-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/python/exported-sql-viewer.py

-#!/usr/bin/env python2
+#!/usr/bin/env python
 # SPDX-License-Identifier: GPL-2.0
 # exported-sql-viewer.py: view data from sql database
 # Copyright (c) 2014-2018, Intel Corporation.