Fix incompatibility of tfds.Builder.as_data_source with MultiSplitInfo. #11500

Job	Run time
Check whether we should run tests or not	10s
Github API tests	2m 26s
Notebook tests	6m 38s
HuggingFace Python 3.10 tests	2m 16s
Core TFDS tests / Generate shards	3s
Core TFDS tests / [Python 3.12][2/4]	6m 23s
Core TFDS tests / [Python 3.10][4/4]	5m 2s
Core TFDS tests / [Python 3.11][2/4]	5m 4s
Core TFDS tests / [Python 3.11][1/4]	6m 30s
Core TFDS tests / [Python 3.12][1/4]	7m 59s
Core TFDS tests / [Python 3.12][4/4]	6m 22s
Core TFDS tests / [Python 3.10][2/4]	5m 6s
Core TFDS tests / [Python 3.11][4/4]	5m 6s
Core TFDS tests / [Python 3.10][1/4]	6m 0s
Core TFDS tests / [Python 3.10][3/4]	7m 24s
Core TFDS tests / [Python 3.11][3/4]	7m 54s
Core TFDS tests / [Python 3.12][3/4]	9m 32s
	1h 29m 55s

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