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

integrate/trapezoidal_test.go

@@ -6,15 +6,15 @@ package integrate
 
 import (
 	"math"
+	"math/rand/v2"
 	"testing"
 
 	"gonum.org/v1/gonum/integrate/testquad"
-	"gonum.org/v1/gonum/internal/rand"
 )
 
 func TestTrapezoidal(t *testing.T) {
 	t.Parallel()
-	rnd := rand.New(rand.NewSource(1))
+	rnd := rand.New(rand.NewPCG(1, 1))
 	for i, test := range []struct {
 		integral testquad.Integral
 		n        int