Revert the changes to Examples/Tests/langmuir/inputs_2d

Examples/Tests/langmuir/inputs_2d

@@ -47,25 +47,16 @@ my_constants.k = 2.*pi/20.e-6  # perturbation wavenumber
 # Particles
 particles.species_names = electrons positrons
 
-# Split the loading of the plasma to test multiple injection sources
-# The two sources s1 and s2 are identical except their zmin and zmax
 electrons.charge = -q_e
 electrons.mass = m_e
-
-electrons.injection_sources = s1 s2
-electrons.s1.injection_style = "NUniformPerCell"
-electrons.s1.zmin = -20.e-6
-electrons.s1.zmax = 0.e-6
-electrons.s2.injection_style = "NUniformPerCell"
-electrons.s2.zmin = 0.e-6
-electrons.s2.zmax = 20.e-6
-
-# These parameters are common to both sources
+electrons.injection_style = "NUniformPerCell"
 electrons.num_particles_per_cell_each_dim = 2 2
 electrons.xmin = -20.e-6
 electrons.xmax =  20.e-6
 electrons.ymin = -20.e-6
 electrons.ymax = 20.e-6
+electrons.zmin = -20.e-6
+electrons.zmax = 20.e-6
 
 electrons.profile = constant
 electrons.density = n0   # number of electrons per m^3