fix: use scalar num of digits on Dataset.load_snapshot (#75)

Review n coordinate when phi is represented by more than one digit #10

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

xcompact3d_toolbox/io.py

@@ -716,7 +716,9 @@ def is_velocity(name):
                 dataset["phi"] = (
                     stack_variables(scalar_variables, stack_scalar=False)
                     .to_array(dim="n")
-                    .assign_coords(n=[int(var[-1]) for var in scalar_variables])
+                    .assign_coords(
+                        n=[int(v[-self.filename_properties.scalar_num_of_digits :]) for v in scalar_variables]
+                    )
                 )
                 set_of_variables -= set(scalar_variables)