fix: Set `tensorboard`'s `global_step` as the default `wandb` x-axis if `sync_tensorboard=True`#20611

Borda merged 3 commits intoLightning-AI:masterLightning-AI/pytorch-lightning:masterfrom

ringohoffman:set-global_step-default-wandb-x-axis-sync_tensorboard=Trueringohoffman/pytorch-lightning:set-global_step-default-wandb-x-axis-sync_tensorboard=TrueCopy head branch name to clipboard