Update link to diktat-ktlint online compare tool (#1782)

Co-authored-by: Paul Dingemans <[email protected]>

docs/install/overview.md

@@ -2,5 +2,5 @@ See [command line interface](cli.md) or [integrations](integrations.md) for deta
 
 ## Online demo
 
-See [`ktlint` online](https://ktlint-demo.herokuapp.com/) if you want to try-out 'ktlint'. This online version compares rule sets provided by `ktlint` and `diktat` (a layer on top of `ktlint`). To contribute to or get more info about `ktlint` online, please visit the [GitHub repository](https://github.com/saveourtool/diktat-demo).
+See [`ktlint` online](https://saveourtool.com/#/demo/diktat) if you want to try-out 'ktlint'. This online version compares rule sets provided by `ktlint` and `diktat` (a layer on top of `ktlint`). To contribute to or get more info about `ktlint` online, please visit the [GitHub repository](https://github.com/saveourtool/diktat-demo).