Update test_optimization.py (glotaran#404)

This fixes some failing optimization test due to a change in lmfit 1.0.1,
where the argument ``max_nfev`` was changed slightly with the intention to
uniformly specify the maximum number of function evalutions (see lmfit PR 610),
this effectively reduces the number of iteration that were run resulting in
a failure to converge within the fixed number of iterations.

Author: jsnel

glotaran/analysis/test/test_optimization.py

@@ -221,7 +221,7 @@ def id():
     assert dataset.data.shape == (cal_axis.size, est_axis.size)
 
     data = {'dataset1': dataset}
-    scheme = Scheme(model=model, parameter=initial, data=data, nfev=5)
+    scheme = Scheme(model=model, parameter=initial, data=data, nfev=10)
 
     result = optimize(scheme)
     print(result.optimized_parameter)