Update "Replace a method with a function" (#5592)

The `replacerFn` parameter is deprecated, with a recommendation to use `callsFake` instead.

Co-authored-by: Jennifer Shehane <[email protected]>

Author: eostrom

docs/api/commands/stub.mdx

@@ -19,7 +19,6 @@ assertion. It is not retryable, chainable, or timeout-able.
 ```javascript
 cy.stub()
 cy.stub(object, method)
-cy.stub(object, method, replacerFn)
 ```
 
 ### Usage
@@ -41,10 +40,6 @@ The `object` that has the `method` to be replaced.
 
 The name of the `method` on the `object` to be wrapped.
 
-<Icon name="angle-right" /> **replacerFn _(Function)_**
-
-The function used to replace the `method` on the `object`.
-
 ### Yields [<Icon name="question-circle"/>](/app/core-concepts/introduction-to-cypress#Subject-Management) {#Yields}
 
 - `cy.stub()` is _synchronous_ and returns a value (the stub) instead of a
@@ -82,7 +77,7 @@ expect(util.addListeners).to.be.called
 // assume App.start calls util.addListeners
 let listenersAdded = false
 
-cy.stub(util, 'addListeners', () => {
+cy.stub(util, 'addListeners').callsFake(() => {
   listenersAdded = true
 })