fix broken links in integration.md (#340)

* fix broken link in integration.md

* fix: broken link to simulator.md file in cosmos-sdk docs

Co-authored-by: Carlos Rodriguez <crodveg@gmail.com>

Author: crodriguezvega

docs/ibc/integration.md

@@ -139,7 +139,7 @@ func NewApp(...args) *App {
 
 ### Module Managers
 
-In order to use IBC, we need to add the new modules to the module `Manager` and to the `SimulationManager` in case your application supports [simulations](./../building-modules/simulator.md).
+In order to use IBC, we need to add the new modules to the module `Manager` and to the `SimulationManager` in case your application supports [simulations](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules/simulator.md).
 
 ```go
 // app.go
@@ -221,4 +221,4 @@ different chains. If you want to have a broader view of the changes take a look
 
 ## Next {hide}
 
-Learn about how to create [custom IBC modules](./custom.md) for your application {hide}
+Learn about how to create [custom IBC modules](./apps.md) for your application {hide}