Update SQL migration guide

Author: MaxGekk

docs/sql-migration-guide.md

@@ -31,7 +31,11 @@ license: |
   - In Spark 3.1, `from_unixtime`, `unix_timestamp`,`to_unix_timestamp`, `to_timestamp` and `to_date` will fail if the specified datetime pattern is invalid. In Spark 3.0 or earlier, they result `NULL`.
 
   - In Spark 3.1, casting numeric to timestamp will be forbidden by default. It's strongly recommended to use dedicated functions: TIMESTAMP_SECONDS, TIMESTAMP_MILLIS and TIMESTAMP_MICROS. Or you can set `spark.sql.legacy.allowCastNumericToTimestamp` to true to work around it. See more details in SPARK-31710.
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+## Upgrading from Spark SQL 3.0 to 3.0.1
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+- In Spark 3.0, JSON datasource and JSON function `schema_of_json` infer TimestampType from string values if they match to the pattern defined by the JSON option `timestampFormat`. Since version 3.0.1, the timestamp type inference is disabled by default. Set the JSON option `inferTimestamp` to `true` to enable such type inference.
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 ## Upgrading from Spark SQL 2.4 to 3.0
 
 ### Dataset/DataFrame APIs