Rephrase documentation of adabelief

[denadai2]

This PR fixes the documentation of total_steps, which enables the warmup only if the value is bigger than zero. However, the documentation says "positive value". Zero (the default value) is positive though

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[bot-of-gabrieldemarmiesse]

@juntang-zhuang

You are owner of some files modified in this pull request.
Would you kindly review the changes whenever you have the time to?
Thank you very much.

[bhack]

I think that it was correct:
http://oeis.org/A000027
http://oeis.org/A001477

[denadai2]

nice. However, "greater than zero" I think requires less expertise to be understood. I thought zero was a positive number for example, and I have a PhD.

[bhack]

There could be some confusion with signed zero but on integer I think it is hard to be confused. I will merge this as it is just an alternative.

[denadai2]

thanks

[juntang-zhuang]

Looks great to me. The same issue is with rectified_adam document

addons/tensorflow_addons/optimizers/rectified_adam.py

Line 107 in 953d848

Enable warmup by setting a positive value.

, you might consider modifying it as well.