Fix typo

See gh-23602

CONTRIBUTING.adoc

@@ -162,7 +162,7 @@ With the requisite Eclipse plugins installed you can select
 If you have performed a checkout of this repository already, use "`File`" -> "`Open`" and
 then select the root `build.gradle` file to import the code.
 
-Alternatively, you can let IntellIJ IDEA checkout the code for you. Use "`File`" ->
+Alternatively, you can let IntelliJ IDEA checkout the code for you. Use "`File`" ->
 "`New`" -> "`Project from Version Control`" and
 `https://github.com/spring-projects/spring-boot` for the URL. Once the checkout has
 completed, a pop-up will suggest to open the project.