remove inexistent features from units.json (#398)

Co-authored-by: Jaquier Aurélien Tristan <aurelien.jaquier@epfl.ch>

Author: AurelienJaquier

efel/units/units.json

@@ -8,11 +8,9 @@
     "AHP_depth_abs_slow": "mV",
     "AHP_depth_diff": "mV",
     "AHP_depth_from_peak": "mV",
-    "AHP_depth_last": "mV",
     "AHP_depth_slow": "mV",
     "AHP_slow_time": "constant",
     "AHP_time_from_peak": "ms",
-    "AHP_time_from_peak_last": "ms",
     "AP1_amp": "mV",
     "AP1_begin_voltage": "mV",
     "AP1_begin_width": "ms",
@@ -68,8 +66,6 @@
     "current_base": "nA",
     "decay_time_constant_after_stim": "ms",
     "depolarized_base": "mV",
-    "diff_max_duringstim": "mV",
-    "diff_min_duringstim": "mV",
     "doublet_ISI": "ms",
     "fast_AHP": "mV",
     "fast_AHP_change": "constant",
@@ -85,13 +81,11 @@
     "inv_time_to_first_spike": "Hz",
     "irregularity_index": "ms",
     "max_amp_difference": "mV",
-    "max_duringstim_from_voltage_base": "mV",
     "maximum_voltage": "mV",
     "maximum_voltage_from_voltagebase": "mV",
     "mean_AP_amplitude": "mV",
     "mean_frequency": "Hz",
     "min_between_peaks_values": "mV",
-    "min_duringstim_from_voltage_base": "mV",
     "min_voltage_between_spikes": "mV",
     "minimum_voltage": "mV",
     "multiple_decay_time_constant_after_stim": "ms",
@@ -115,7 +109,6 @@
     "steady_state_hyper": "mV",
     "steady_state_voltage": "mV",
     "steady_state_voltage_stimend": "mV",
-    "steady_state_voltage_stimend_from_voltage_base": "mV",
     "strict_burst_mean_freq": "Hz",
     "strict_burst_number": "constant",
     "strict_interburst_voltage": "mV",