test_matplotlib_export: Add import numpy to intro code

Numpy 2.0 changes scalar repr: https://numpy.org/neps/nep-0051-scalar-representation.html

Author: ales-erjavec

Orange/widgets/tests/test_matplotlib_export.py

@@ -11,6 +11,7 @@
 
 def add_intro(a):
     r = "import matplotlib.pyplot as plt\n" + \
+        "import numpy as np\n" + \
         "from numpy import array\n" + \
         "plt.clf()"
     return r + a