Only set accurate operation name in `litellm`

[alexander-alderman-webb]

Using a fallback leads to wrong data

sentry-python/sentry_sdk/integrations/litellm.py

Lines 90 to 97 in b4e0367

	# Start a new span/transaction
	span = get_start_span_function()(
	op=(
	consts.OP.GEN_AI_CHAT
	if operation == "chat"
	else consts.OP.GEN_AI_EMBEDDINGS
	),
	name=f"{operation} {model}",

[linear-code]

PY-2501