support/scripts/check-uniq-files: remove csv module import

Since commit 5563a1c6a48716debe2983869ddb757318094dce
("support/check-uniq-files: support weird locales and filenames"), the
'csv' Python module is no longer used by the check-uniq-files.

Due to this, flake8 complains with:

support/scripts/check-uniq-files:4:1: F401 'csv' imported but unused

Fix this by dropping the useless csv import.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/scripts/check-uniq-files

@@ -1,7 +1,6 @@
 #!/usr/bin/env python
 
 import sys
-import csv
 import argparse
 from collections import defaultdict