Add steps argument to Predator Prey exercise code

[Robadob]

Argument is mandatory, and requires a positive integer, previously defaulted to 250.

Minimal args in similar style to earlier travelling sales person script.

Closes #83

[github-actions]

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🔍 Inspect the changes: https://github.com/RSE-Sheffield/pando-python/compare/md-outputs..md-outputs-PR-84

The following changes were observed in the rendered markdown documents:

 files/pred-prey/predprey.py | 13 ++++++++++---
 md5sum.txt                  |  4 ++--
 profiling-functions.md      |  5 ++---
 profiling-lines.md          | 10 +++-------
 4 files changed, 17 insertions(+), 15 deletions(-)

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⏱️ Updated at 2025-05-10 19:22:24 +0000

[JostMigenda]

LGTM, just some minor bits of cleanup.

[Robadob]

Thanks for the brilliant review as always @JostMigenda, I obviously did a low effort job putting this together given I didn't even catch the fact I should import sys !.

Happy for you to approve and squash.