A million deaths assuming they reduce carbon emissions equally would only be 0.0125%. In reality considering that vaccines are unevenly distributed in favor of countries with high CO2 emissions, it's likely much less than that.
Most deaths are of old people who had few years to live. They were also not consuming much. And they would not have more children. The CO2 impact of these deaths is negligible if not positive (in the bad sense) because the disruption of Covid will end up emitting more CO2 than business as usual (a lot of investment could have been used to fight climate change but were diverted to fight Covid and to support the industries that are the most in troubles (which are the most polluting ones).
Death don't have a great effect as the general carbon production (oil, coal, gas) are still rising.