[CLN] Remove legacy backend and unused code

Eliminated "aesara" and "legacy" backends from the config and compute logic. Cleaned up redundant code, improving codebase maintainability and clarity by focusing on supported backends.

Author: Leguark

gempy/API/compute_API.py

@@ -56,9 +56,6 @@ def compute_model(gempy_model: GeoModel, engine_config: Optional[GemPyEngineConf
                 data_descriptor=gempy_model.input_data_descriptor,
                 geophysics_input=gempy_model.geophysics_input,
             )
-
-        case AvailableBackends.aesara | AvailableBackends.legacy:
-            gempy_model.legacy_model = _legacy_compute_model(gempy_model)
         case _:
             raise ValueError(f'Backend {engine_config} not supported')
 
@@ -189,9 +186,3 @@ def _check_convergence_criterion(conditional_number: float, condition_number_old
     return geo_model.solutions
 
 
-def _legacy_compute_model(gempy_model: GeoModel) -> 'gempy_legacy.Project':
-    gpl = require_gempy_legacy()
-    legacy_model: gpl.Project = gempy3_to_gempy2(gempy_model)
-    gpl.set_interpolator(legacy_model)
-    gpl.compute_model(legacy_model)
-    return legacy_model