Bump sqlglot from 20.3.0 to 20.4.0

Bumps sqlglot from 20.3.0 to 20.4.0.

Commits

• 4217284 fix: bigquery update set null
• 5624fdb feat(optimizer): simplify date comparisons (#2710)
• 6868336 fix: clickhouse final table name closes #2711
• c5b967c avoid unnecessary copy for table names
• 8a5021c Feat: transpile Trino unicode to \u... strings (Spark, Snowflake) (#2709)
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