fix docs for .sync until fixed in vue core, fixes #1721

Author: chrisvfritz

src/v2/guide/components-custom-events.md

@@ -136,7 +136,7 @@ Now the `<base-input>` component is a **fully transparent wrapper**, meaning it
 
 In some cases, we may need "two-way binding" for a prop. Unfortunately, true two-way binding can create maintenance issues, because child components can mutate the parent without the source of that mutation being obvious in both the parent and the child.
 
-That's why instead, we recommend emitting events in the pattern of `update:my-prop-name`. For example, in a hypothetical component with a `title` prop, we could communicate the intent of assigning a new value with:
+That's why instead, we recommend emitting events in the pattern of `update:myPropName`. For example, in a hypothetical component with a `title` prop, we could communicate the intent of assigning a new value with:
 
 ```js
 this.$emit('update:title', newTitle)