Fix correspondence between solution code and exercise template

Issue marijnh#475

Author: marijnh

code/solutions/08_1_retry.js

@@ -1,10 +1,10 @@
-function MultiplicatorUnitFailure() {}
+class MultiplicatorUnitFailure extends Error {}
 
 function primitiveMultiply(a, b) {
-  if (Math.random() < 0.5) {
+  if (Math.random() < 0.2) {
     return a * b;
   } else {
-    throw new MultiplicatorUnitFailure();
+    throw new MultiplicatorUnitFailure("Klunk");
   }
 }
 
@@ -21,4 +21,3 @@ function reliableMultiply(a, b) {
 
 console.log(reliableMultiply(8, 8));
 // → 64
-