Rough workaround to fix CI error

CI was failing when calling the new injection_helper_functions module as
anaconda attempted to update numpy (unknown reason)

pyfstat/__init__.py

@@ -3,5 +3,3 @@ from __future__ import division as _division
 from .core import BaseSearchClass, ComputeFstat, Writer, SemiCoherentSearch, SemiCoherentGlitchSearch
 from .mcmc_based_searches import MCMCSearch, MCMCGlitchSearch, MCMCSemiCoherentSearch, MCMCFollowUpSearch, MCMCTransientSearch
 from .grid_based_searches import GridSearch, GridUniformPriorSearch, GridGlitchSearch, FrequencySlidingWindow
-from .injection_helper_functions import get_frequency_range_of_signal
-