The state fund that gives first-responders overdose reversal agent naloxone at a discounted rate had been depleted, but just received a $300,000 boost from Attorney General Maura Healey and a private donation.RIZE Massachusetts — a nonprofit launched by medical giant Partners HealthCare and General Electric to combat the opioid crisis — announced a $50,000 contribution yesterday following reports that the state’s Municipal Naloxone Bulk Purchasing Trust Fund ran dry last fall.