[test] fix missing import

src/pymortests/vectorarray.py

@@ -14,6 +14,7 @@
 from pymor.vectorarrays.interface import VectorSpace
 from pymor.vectorarrays.numpy import NumpyVectorSpace
 from pymor.tools.floatcmp import float_cmp, bounded
+from pymor.tools.random import new_rng
 from pymortests.base import might_exceed_deadline
 from pymortests.pickling import assert_picklable_without_dumps_function
 import pymortests.strategies as pyst