Simplify translating local variable definitions in C tests to Python

[eerovaher]

The TestFunction class in erfa_generator is responsible for translating a C file with ERFA tests into a test suite for pytest. The code responsible for translating local variable definitions to Python is now shorter. There are a few differences between the erfa/tests/test_ufunc.py generated by current main branch and this PR:

550c550
<     b = np.empty(3, erfa_ufunc.dt_eraLDBODY).view(np.recarray)
---
>     b = np.empty((3,), erfa_ufunc.dt_eraLDBODY).view(np.recarray)
652c652
<     b = np.empty(3, erfa_ufunc.dt_eraLDBODY).view(np.recarray)
---
>     b = np.empty((3,), erfa_ufunc.dt_eraLDBODY).view(np.recarray)
1897c1897
<     b = np.empty(3, erfa_ufunc.dt_eraLDBODY).view(np.recarray)
---
>     b = np.empty((3,), erfa_ufunc.dt_eraLDBODY).view(np.recarray)

But these differences are not important because np.empty() interprets both the integer 3 and the single element tuple (3,) to mean the same shape.