Prefer router.replace if you delete sth.

@ogerly, this is a perfect example where `this.$router.replace` makes a
lot more sense that `this.$router.push`. When you go back in your browser
history, you won't get 404 not found error.

webapp/components/Modal/DeleteUserModal.vue

@@ -142,7 +142,7 @@ export default {
             setTimeout(() => {
               this.success = false
               this.$emit('close')
-              this.$router.history.push('/')
+              this.$router.history.replace('/')
             }, 500)
           }, 1500)
           this.loading = false