[Python] Remove Scalar legacy cast from Cython test

[llama90]

Describe the enhancement requested

This is a sub-issue of the issue mentioned below.

• [C++] Deprecate Scalar::CastTo #39182

To resolve the main issue, we need to replace it with Cast or remove the legacy CastTo from Cython.

To solve the main issue better, this should come before the main issue.

• arrow/python/pyarrow/includes/libarrow.pxd

  Line 1155 in 0ce54b6

  CResult[shared_ptr[CScalar]] CastTo(shared_ptr[CDataType] to) const

• arrow/python/pyarrow/tests/pyarrow_cython_example.pyx

  Line 53 in 0ce54b6

  c_result = c_scalar.get().CastTo(c_type)

error message in the python workflow

----------------------------- Captured stderr call -----------------------------
pyarrow_cython_example.cpp:8782:46: error: no member named 'CastTo' in 'arrow::Scalar'
  __pyx_v_c_result = __pyx_v_c_scalar.get()->CastTo(__pyx_v_c_type);
                     ~~~~~~~~~~~~~~~~~~~~~~  ^
1 error generated.
error: command '/usr/bin/clang' failed with exit code 1

Component(s)

Python

[llama90]

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