closes #514

Removing this restriction allows literals like date/time to be used in criteria queries.

The following is valid Sql that should be allowed 💯

UPDATE test
SET date1 = CURRENT_TIMESTAMP,
    date2 = CURRENT_TIME,
    date3 = CURRENT_TIMESTAMP
WHERE date1 > CURRENT_TIME;

⚠️ I have tested this with SqlDelight using the publishLocalToMaven with the current snapshot. 📷
However, SqlDelight is using sql-psi 0.4.3 and this current 0.5.0-Snapshot is not compatible (as expected semantically) with SqlDelight. e.g https://github.com/cashapp/sqldelight/blob/master/sqldelight-compiler/src/main/kotlin/app/cash/sqldelight/core/SqlDelightEnvironment.kt#L75 and https://github.com/AlecStrong/sql-psi/blob/master/core/src/main/kotlin/com/alecstrong/sql/psi/core/SqlCoreEnvironment.kt#L68

Either changes should be made on top of 0.4.3 or wait for 0.5.0 to be integrated into SqlDelight ⚔️

Found this 0.5.0 release to be integrated with SqlDelight 🏒 🥅 and appears to fix the breaking differences
sqldelight/sqldelight#4283 (comment) - so can wait for that to be merged 🧜