[MLLIB] Fix CholeskyDecomposition assertion's message

Change assertion's message so it's consistent with the code. The old message says that the invoked method was lapack.dports, where in fact it was lapack.dppsv method.

Author: Wojciech Jurczyk <wojtek.jurczyk@gmail.com>

Closes #10818 from wjur/wjur/rename_error_message.

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

@@ -37,7 +37,7 @@ private[spark] object CholeskyDecomposition {
     val info = new intW(0)
     lapack.dppsv("U", k, 1, A, bx, k, info)
     val code = info.`val`
-    assert(code == 0, s"lapack.dpotrs returned $code.")
+    assert(code == 0, s"lapack.dppsv returned $code.")
     bx
   }