update link to our checkstyle rules file (#278)

which was moved to an external repository in c0115ff & f118b25

config/ide/README.md

@@ -14,4 +14,4 @@ Please use this [guide](https://help.eclipse.org/neon/index.jsp?topic=%2Forg.ecl
 
 [Checkstyle](http://checkstyle.sourceforge.net/) can check if Java code complies to a given set of code style rules. It can be used stand alone, but there are also plugins for IDEs like [intelliJ](https://plugins.jetbrains.com/plugin/1065-checkstyle-idea) and [eclipse](http://checkstyle.org/eclipse-cs/), or for build tools like [maven](https://maven.apache.org/plugins/maven-checkstyle-plugin/).
 
-For checkstyle, use the dedicated [checkstyle-google-oshdb.xml](/config/ide/checkstyle-google-oshdb.xml) configuration file.
+For checkstyle, use our dedicated [checkstyle-google-ohsome.xml](https://gitlab.gistools.geog.uni-heidelberg.de/giscience/big-data/ohsome/parent/-/blob/master/ohsome-codestyle/src/main/resources/checkstyle-google-ohsome.xml) configuration file.