gn2bp: Remove unused imports

Test: ./update_results.sh
Change-Id: Ie868d599fe8ad8024ca188ec24d87106a363a8cf
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index cf8f1dd..dbfa422 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -26,7 +26,6 @@
 # libraries are also mapped to their Android equivalents -- see |builtin_deps|.
 
 import argparse
-import collections
 import json
 import logging as log
 import operator
diff --git a/tools/gn2bp/gn_utils.py b/tools/gn2bp/gn_utils.py
index 919b3e3..5f187a3 100644
--- a/tools/gn2bp/gn_utils.py
+++ b/tools/gn2bp/gn_utils.py
@@ -15,17 +15,10 @@
 # A collection of utilities for extracting build rule information from GN
 # projects.
 
-from __future__ import print_function
-import collections
-import errno
-import filecmp
 import json
 import logging as log
 import os
 import re
-import shutil
-import subprocess
-import sys
 
 BUILDFLAGS_TARGET = '//gn:gen_buildflags'
 GEN_VERSION_TARGET = '//src/base:version_gen_h'