Actually fix that unit

The definition needed a number.

macrovision.js

@@ -243,7 +243,7 @@ math.createUnit("nanoacres", {
     prefixes: "long"
 })
 math.createUnit("barnMegaparsecs", {
-    definition: "barn megaparsec",
+    definition: "1 barn megaparsec",
     prefixes: "long"
 })
 math.createUnit("firkins", {