Update CHANGELOG (#639)

Author: mbleigh

CHANGELOG.md

@@ -1,11 +1,11 @@
 - Adds support for defining max number of instances for a function. Example:
 
-```
-functions.runWith({
-  maxInstances: 10
-}).https.onRequest(...);
-```
+  ```
+  functions.runWith({
+    maxInstances: 10
+  }).https.onRequest(...);
+  ```
 
-Learn more about max instances in the [Google Cloud documentation.](https://cloud.google.com/functions/docs/max-instances)
+  Learn more about max instances in the [Google Cloud documentation.](https://cloud.google.com/functions/docs/max-instances)
 
 - Fixes TypeScript build error when `package-lock.json` is present by updating dependencies (Issue #637).