Numeric: fix scale check for bqnumeric (#1723)

For bigquery we were checking for numeric scale being < precision, also
need to make sure it is less than 20 as that is the scale we set for
bignumeric in bq

flow/datatypes/numeric.go

@@ -61,15 +61,15 @@ func (BigQueryNumericCompatibility) MaxPrecision() int16 {
 }
 
 func (BigQueryNumericCompatibility) MaxScale() int16 {
-	return 37
+	return 20
 }
 
 func (BigQueryNumericCompatibility) DefaultPrecisionAndScale() (int16, int16) {
 	return PeerDBBigQueryPrecision, PeerDBBigQueryScale
 }
 
 func (BigQueryNumericCompatibility) IsValidPrevisionAndScale(precision, scale int16) bool {
-	return precision > 0 && precision <= 38 && scale < precision
+	return precision > 0 && precision <= 38 && scale <= 20 && scale < precision
 }
 
 type DefaultNumericCompatibility struct{}