all: replace internal rand shim with math/rand/v2

lapack/testlapack/dpbcon.go

@@ -7,11 +7,11 @@ package testlapack
 import (
 	"fmt"
 	"math"
+	"math/rand/v2"
 	"testing"
 
 	"gonum.org/v1/gonum/blas"
 	"gonum.org/v1/gonum/floats"
-	"gonum.org/v1/gonum/internal/rand"
 	"gonum.org/v1/gonum/lapack"
 )
 
@@ -25,7 +25,7 @@ type Dpbconer interface {
 // checking that the estimated condition number is not too different from the
 // condition number computed via the explicit inverse of A.
 func DpbconTest(t *testing.T, impl Dpbconer) {
-	rnd := rand.New(rand.NewSource(1))
+	rnd := rand.New(rand.NewPCG(1, 1))
 	for _, n := range []int{0, 1, 2, 3, 4, 5, 10, 50} {
 		for _, kd := range []int{0, (n + 1) / 4, (3*n - 1) / 4, (5*n + 1) / 4} {
 			for _, uplo := range []blas.Uplo{blas.Upper, blas.Lower} {