docs: fix documented parameter names that do not match the signature

[massimiliano1991]

What

Three docstrings document a parameter name that does not exist in the function signature:

location	documented	actual
utils/operations.py recursively_apply	main_type	test_type
tracking.py SwanLabTracker.log	data	values
tracking.py MLflowTracker.log_figure	**kwargs	**save_kwargs

Why it's worth fixing

For the first two the mismatch is not only cosmetic. Both functions accept **kwargs, so a
keyword copied from the documentation is not rejected at the boundary — it is swallowed and
forwarded to the user's own callback:

>>> recursively_apply(my_fn, data, main_type=torch.Tensor)   # as documented
TypeError: my_fn() got an unexpected keyword argument 'main_type'

The traceback names my_fn, not recursively_apply, so nothing points back to the docstring
that suggested the argument.

recursively_apply's docstring also describes main_type as a type defaulting to
torch.Tensor, while test_type is a predicate defaulting to is_torch_tensor. The three
other references to main_type in the same docstring (including the Returns: line) are
updated to match.

For MLflowTracker.log_figure the ** form absorbs any name, so there is no error — but the
docstring also pointed at mlflow.log_image rather than mlflow.log_figure. The surrounding
Args: block had its description lines un-indented, which breaks rendering, so those lines are
re-indented to the style used by the rest of the file. SwanLabTracker.log had the same issue
and now matches the other trackers' log methods in that module.

How these were found

Mechanically: parsing each Args: block and diffing it against the ast signature, then
checking each hit by hand. Only these three came out as documented-but-absent across
src/accelerate.

Checks

• docs only — no behaviour change, no public API touched
• ruff format --check clean on both files; ruff check reports only pre-existing findings in
  untouched lines