More aggressive GC to prevent matplotlib memory issues

backend/scripts/acoustics.py

backend/scripts/ahrs_calibration.py

backend/scripts/dom_activity.py

backend/scripts/dom_rates.py

backend/scripts/live_triggermap.py

backend/scripts/log_analyser.py

backend/scripts/pmt_rates.py

backend/scripts/rttc.py

backend/scripts/time_residuals.py

backend/scripts/trigger_rates.py

backend/scripts/triggered_hits.py

backend/scripts/ztplot.py