Fixup yarn update -> yarn upgrade (#374)

jgable · web-flow · commit 9003545e7d3e · 2021-11-01T15:46:40.000-06:00
Docs for yarn upgrade here; https://classic.yarnpkg.com/lang/en/docs/cli/upgrade/
diff --git a/MIGRATION_GUIDE.md b/MIGRATION_GUIDE.md
@@ -6,7 +6,7 @@ If you’re using  `analytics-react-native 1.5.1`  or older, follow these steps
 1. Update existing package
 
 ```sh
-yarn update @segment/analytics-react-native@2.0
+yarn upgrade @segment/analytics-react-native@2.0
 ```
 2. Add/Update pods
 ```sh

-Original file line number
+Diff line change
 . Update existing package
 ```sh
 -yarn update @segment/[email protected]
 +yarn upgrade @segment/[email protected]
 ```
 . Add/Update pods
 ```sh