[Bug]: Potential bug in TorchRunningMeanStd

[dominikonysz]

During my debugging I came across the computation of the updated value for the running mean:

rllte/rllte/common/utils.py

Line 80 in 5b984b0

new_mean = mean + delta + batch_count / tot_count

It doesn't really influence me as I'm not using it right now but I feel like it should instead be:

new_mean = mean + delta * batch_count / tot_count 

[yuanmingqi]

@roger-creus Hi Roger, can you check this issue?

[yuanmingqi]

@dominikonysz We have uploaded the update and marked you as a co-author. Thank you for the issue.