Update CONTRIBUTING.adoc

Update repository URL in IDE setup instructions

Author: maciejkopecpl

CONTRIBUTING.adoc

@@ -88,7 +88,7 @@ then select the root `build.gradle` file to import the code.
 
 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
+`https://github.com/springdoc/springdoc-openapi.git` for the URL. Once the checkout has
 completed, a pop-up will suggest to open the project.