docs(notebooks): fix cell center for Simple MODFLOW 6 Model (#2013)

.docs/Notebooks/mf6_simple_model_example.py

@@ -125,7 +125,7 @@
 # must be entered as a tuple as the first entry.
 # Remember that these must be zero-based indices!
 chd_rec = []
-chd_rec.append(((0, int(N / 4), int(N / 4)), h2))
+chd_rec.append(((0, int(N / 2), int(N / 2)), h2))
 for layer in range(0, Nlay):
     for row_col in range(0, N):
         chd_rec.append(((layer, row_col, 0), h1))