Fix elastic modeling #844

Job	Run time
list-examples	4s
examples/machine-learning/example_born_fully_connected.jl	5m 38s
examples/machine-learning/example_extended_source.jl	5m 36s
examples/machine-learning/example_extended_source_cnn.jl	5m 55s
examples/scripts/extended_source_lsqr.jl	5m 29s
examples/scripts/fwi_example_2D.jl	5m 50s
examples/scripts/fwi_example_ADloss.jl	5m 50s
examples/scripts/fwi_example_NLopt.jl	5m 52s
examples/scripts/fwi_example_constraints.jl	6m 15s
examples/scripts/fwi_example_minConf.jl	5m 35s
examples/scripts/fwi_example_studentst.jl	5m 45s
examples/scripts/fwi_gauss_newton.jl	1m 52s
examples/scripts/illum.jl	1m 53s
examples/scripts/imaging_conditions.jl	1m 35s
examples/scripts/lsrtm_2D.jl	1m 32s
examples/scripts/modeling_basic_2D.jl	1s
examples/scripts/modeling_basic_3D.jl	1m 28s
examples/scripts/modeling_basic_elastic.jl	1m 21s
examples/scripts/modeling_extended_source_2D.jl	1m 37s
examples/scripts/modeling_extended_source_3D.jl	1s
examples/scripts/modeling_medical_2D.jl	1s
examples/scripts/modeling_wavefields_2D.jl	1s
examples/scripts/splsrtm_2D.jl	1s
	1h 9m 12s

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