Rename snapshots for `test_add_time_expr` #4547

Job	Run time
MetricFlow Tests (PostgreSQL)	2m 32s
MetricFlow Tests (DuckDB) (3.9)	2m 59s
MetricFlow Tests (DuckDB) (3.12)	2m 50s
MetricFlow Packages Tests (3.9)	3m 23s
MetricFlow Packages Tests (3.12)	3m 23s
MetricFlow Unit Tests	1s
	15m 8s

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