Fixed typo on implementation notes page (#9258)

Added paren to "mountComponent()" for consistency

contributing/implementation-notes.md

@@ -875,7 +875,7 @@ This document is simplified compared to the real codebase. There are a few impor
 * [`ReactCompositeComponent`](https://github.com/facebook/react/blob/83381c1673d14cd16cf747e34c945291e5518a86/src/renderers/shared/stack/reconciler/ReactCompositeComponent.js) is the equivalent of `CompositeComponent` in this tutorial. It handles calling user-defined components and maintaining their state.
 * [`instantiateReactComponent`](https://github.com/facebook/react/blob/83381c1673d14cd16cf747e34c945291e5518a86/src/renderers/shared/stack/reconciler/instantiateReactComponent.js) contains the switch that picks the right internal instance class to construct for an element. It is equivalent to `instantiateComponent()` in this tutorial.
 
-* [`ReactReconciler`](https://github.com/facebook/react/blob/83381c1673d14cd16cf747e34c945291e5518a86/src/renderers/shared/stack/reconciler/ReactReconciler.js) is a wrapper with `mountComponent`, `receiveComponent()`, and `unmountComponent()` methods. It calls the underlying implementations on the internal instances, but also includes some code around them that is shared by all internal instance implementations.
+* [`ReactReconciler`](https://github.com/facebook/react/blob/83381c1673d14cd16cf747e34c945291e5518a86/src/renderers/shared/stack/reconciler/ReactReconciler.js) is a wrapper with `mountComponent()`, `receiveComponent()`, and `unmountComponent()` methods. It calls the underlying implementations on the internal instances, but also includes some code around them that is shared by all internal instance implementations.
 
 * [`ReactChildReconciler`](https://github.com/facebook/react/blob/83381c1673d14cd16cf747e34c945291e5518a86/src/renderers/shared/stack/reconciler/ReactChildReconciler.js) implements the logic for mounting, updating, and unmounting children according to the `key` of their elements.