Extend arctan cutoff point to lower-precision value to fix issues with TR sensors' phase calculation

Because the response curves produced by TR sensors have amplitudes lower than 1E-16 before scaling by gain values, the arctan calculation for these responses fails when running the unscaled response curve generation. Extending out the cutoff value to 1E-25 will fix this issue. This is the cause of the bug seen here: https://igskgacgvmaslwb.cr.usgs.gov/rt/Ticket/Display.html?id=17504