update migration guide

Author: Ngone51

docs/sql-migration-guide.md

@@ -40,8 +40,6 @@ license: |
 
 ### DDL Statements
 
-  - In Spark 3.0, `CREATE TABLE` without a specific provider uses the value of `spark.sql.sources.default` as its provider. In Spark version 2.4 and below, it was Hive. To restore the behavior before Spark 3.0, you can set `spark.sql.legacy.createHiveTableByDefault.enabled` to `true`.
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   - In Spark 3.0, when inserting a value into a table column with a different data type, the type coercion is performed as per ANSI SQL standard. Certain unreasonable type conversions such as converting `string` to `int` and `double` to `boolean` are disallowed. A runtime exception is thrown if the value is out-of-range for the data type of the column. In Spark version 2.4 and below, type conversions during table insertion are allowed as long as they are valid `Cast`. When inserting an out-of-range value to an integral field, the low-order bits of the value is inserted(the same as Java/Scala numeric type casting). For example, if 257 is inserted to a field of byte type, the result is 1. The behavior is controlled by the option `spark.sql.storeAssignmentPolicy`, with a default value as "ANSI". Setting the option as "Legacy" restores the previous behavior.
 
   - The `ADD JAR` command previously returned a result set with the single value 0. It now returns an empty result set.