[SPARK-9912] [MLLIB] QRDecomposition should use QType and RType for type names...

[SPARK-9912] [MLLIB] QRDecomposition should use QType and RType for type names instead of UType and VType

hhbyyh

Author: Xiangrui Meng <meng@databricks.com>

Closes #8140 from mengxr/SPARK-9912.

mllib/src/main/scala/org/apache/spark/mllib/linalg/SingularValueDecomposition.scala

@@ -31,5 +31,5 @@ case class SingularValueDecomposition[UType, VType](U: UType, s: Vector, V: VTyp
  * Represents QR factors.
  */
 @Experimental
-case class QRDecomposition[UType, VType](Q: UType, R: VType)
+case class QRDecomposition[QType, RType](Q: QType, R: RType)