The following accumulators/window functions potentially unnecessarily narrow values

• stdDev Accumulator – https://github.com/mongodb/mongo/blob/23887691c018923b054dd19e7ac255981524bf1c/src/mongo/db/pipeline/accumulator.h#L348-L351
• stdDev WindowFunction – https://github.com/mongodb/mongo/blob/23887691c018923b054dd19e7ac255981524bf1c/src/mongo/db/pipeline/window_function/window_function_stddev.h#L78 – note internal uses RemovableSum which i'd suspect could lead to different result by comparison to the accumulator