Replace geant_sid with gs_id

gso/cli/imports.py

gso/workflows/l2_circuit/create_imported_layer_2_circuit.py

gso/workflows/l2_circuit/create_layer_2_circuit.py

...kflows/l3_core_service/create_imported_l3_core_service.py

gso/workflows/l3_core_service/create_l3_core_service.py

gso/workflows/l3_core_service/modify_l3_core_service.py

test/cli/test_imports.py

test/fixtures/l3_core_service_fixtures.py

test/fixtures/layer_2_circuit_fixtures.py

test/workflows/iptrunk/test_create_iptrunk.py

...kflows/l2_circuit/test_create_imported_layer_2_circuit.py

test/workflows/l2_circuit/test_create_layer_2_circuit.py

...s/l3_core_service/test_create_imported_l3_core_service.py

.../workflows/l3_core_service/test_create_l3_core_service.py

.../workflows/l3_core_service/test_modify_l3_core_service.py