docs(firestore-shorten-urls-bitly): changed Bit.ly to Bitly in PREINSTALL file (#210)

Author: rachelsaunders

firestore-shorten-urls-bitly/PREINSTALL.md

@@ -13,7 +13,7 @@ This extension uses Bitly to shorten URLs, so you'll need to supply your Bitly a
 
 Before installing this extension, make sure that you've [set up a Cloud Firestore database](https://firebase.google.com/docs/firestore/quickstart) in your Firebase project.
 
-You must also have a Bit.ly account and access token before installing this extension.
+You must also have a Bitly account and access token before installing this extension.
 
 #### Billing
 
@@ -24,4 +24,4 @@ This extension uses other Firebase or Google Cloud Platform services which may h
 
 When you use Firebase Extensions, you're only charged for the underlying resources that you use. A paid-tier billing plan is only required if the extension uses a service that requires a paid-tier plan, for example calling to a Google Cloud Platform API or making outbound network requests to non-Google services. All Firebase services offer a free tier of usage. [Learn more about Firebase billing.](https://firebase.google.com/pricing)
 
-Usage of this extension also requires you to have a Bit.ly account. You are responsible for any associated costs with your usage of Bit.ly.
+Usage of this extension also requires you to have a Bitly account. You are responsible for any associated costs with your usage of Bitly.