Fix link in "Vaadin Spring Tips" article (#11214)

Link to `3.0` branch of `vaadin/spring` which is the latest version for Vaadin 8 and latest version branch to contain this mentioned file with this path/name.

documentation/articles/VaadinSpringTips.asciidoc

@@ -22,4 +22,4 @@ example which can be configured:
 * `vaadin.servlet.closeIdleSessions=true`
 
 For full list of available properties, see
-https://github.com/vaadin/spring/blob/master/vaadin-spring-boot/src/main/java/com/vaadin/spring/boot/internal/VaadinServletConfigurationProperties.java[VaadinServletConfigurationProperties].
+https://github.com/vaadin/spring/blob/3.0/vaadin-spring-boot/src/main/java/com/vaadin/spring/boot/internal/VaadinServletConfigurationProperties.java[VaadinServletConfigurationProperties].