Remove unnecessary TODO comment in fit_loop.py (#21265)

* Initial plan

* Remove unnecessary TODO comment in fit_loop.py

The TODO suggested moving max_steps check inside training loop, but this is
correctly placed in fit_loop since global_step tracks steps across epochs
and the fit_loop is responsible for deciding when to stop the entire fit
process. Moving it would require additional flag variables, making the code
more complex without any benefit.

Co-authored-by: Borda <6035284+Borda@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Borda <6035284+Borda@users.noreply.github.com>
Co-authored-by: Deependu <deependujha21@gmail.com>