Update polybase-troubleshooting.md

Added Row width limit

Author: Ckarst

docs/relational-databases/polybase/polybase-troubleshooting.md

@@ -218,7 +218,7 @@ manager: "jhubbard"
  ## Known Limitations
  
  PolyBase has the following limitations: 
- - The maximum possible row size, including the full length of variable length columns, can not exceed 1 MB. 
+ - The maximum possible row size, including the full length of variable length columns, can not exceed 32 KB in SQL Server or 1 MB in     Azure SQL Data Warehouse. 
  - PolyBase doesn’t support the Hive 0.12+ data types (i.e. Char(), VarChar())   
  - When exporting data into an ORC File Format from SQL Server or Azure SQL Data Warehouse text heavy columns can be limited to as few as 50 columns due to java out of memory errors. To work around this, export only a subset of the columns.
  - Cannot Read or Write data encrypted at rest in Hadoop. This includes HDFS Encrypted Zones or Transparent Encryption.