Solved minor bug with MLFlow logger

[BrianPulfer]

Resolves #16411 the minor issue #16411 (typo) from

params_list.append(Param(key=v, value=v))

to

params_list.append(Param(key=k, value=v))

[senarvi]

For me this fixes MLflow logging.

But now that I look at the code, what do you think of replacing the entire loop with this:

params_list = [Param(key=k, value=str(v)[:250]) for k, v in params.items()]

i.e. instead of not logging long string values, we would log the first 250 characters?

[awaelchli]

@senarvi That sounds good to me. Feel free to send a PR with this improvement. Fewer warnings are always better if it can be avoided :)

[schmidt-jake]

@senarvi thanks for catching this! LGTM.

As for your suggestion, two thoughts:

1. Truncating keys to 250 characters may result in duplicate keys — thoughts on how to handle this?
2. MLFlow version 1.28 increased the max param length to 500 — would be nice to take advantage of this

Also — should we have key=str(k) to be safe?