Removed unused import 'collections'

NanoVNASaver/NanoVNASaver.py

@@ -13,7 +13,6 @@
 #
 #  You should have received a copy of the GNU General Public License
 #  along with this program.  If not, see <https://www.gnu.org/licenses/>.
-import collections
 import logging
 import math
 import sys