Fix typo. in README.md (jestjs#3635)

Author: agiron123

danger/README.md

@@ -1,6 +1,6 @@
 ## Why?
 
-As Danger uses jest-runtime we need to separate out node_modules for Danger into it's own folder as conflicts [occured](https://github.com/facebook/jest/pull/2532).
+As Danger uses jest-runtime we need to separate out node_modules for Danger into it's own folder as conflicts [occurred](https://github.com/facebook/jest/pull/2532).
 
 If you'd like to make changes to the Dangerfile, find an existing PR and copy the URL.