docs: add note on TorchMetrics integration for logging best practices

[bhimrazy]

What does this PR do?

Closes #18282

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📚 Documentation preview 📚: https://pytorch-lightning--21103.org.readthedocs.build/en/21103/

[bhimrazy]

Link issue seems to come from

pytorch-lightning/docs/source-pytorch/conf.py

Lines 129 to 131 in ff64a92

	adjust_linked_external_docs(
	"https://lightning.ai/docs/torchmetrics", "https://lightning.ai/docs/torchmetrics/v{torchmetrics.__version__}/", _PATH_ROOT, version_digits=3
	)

Ideally I think it should be https://lightning.ai/docs/torchmetrics/stable/