improve inc_subtensor docstring
improve inc_subtensor docstring

FighterLYL/cgt,hojonathanho/cgt,bstadie/cgt,hojonathanho/cgt,jiumem/cgt,rohanraja/cgt_distributed,davmre/cgt,briancheung/cgt,nickjhay/cgt,dementrock/cgt,rohanraja/cgt_distributed,nickjhay/cgt,FighterLYL/cgt,rohanraja/cgt_distributed,mesnilgr/cgt,animesh-garg/cgt,RichardWarfield/cgt,jiumem/cgt,nebw/cgt,davmre/cgt,nebw/cgt,bstadie/cgt,briancheung/cgt,nickjhay/cgt,dementrock/cgt,FighterLYL/cgt,RichardWarfield/cgt,RichardWarfield/cgt,nebw/cgt,rohanraja/cgt_distributed,bstadie/cgt,dementrock/cgt,animesh-garg/cgt,hojonathanho/cgt,jiumem/cgt,davmre/cgt,briancheung/cgt,animesh-garg/cgt,mesnilgr/cgt,mesnilgr/cgt