docs: fix heroku link (requarks#25)

* fix link

* Update heroku.md

Co-authored-by: Nicolas Giard <[email protected]>

Author: mio-19

install/heroku.md

@@ -16,7 +16,7 @@ A preconfigured deploy template is provided for convenience:
 
 # Important Notes
 
-- The deployment template will use the default PostgreSQL plan, which is the Hobby Dev (free) plan. You can upgrade to a larger plan afterwards as detailed in the [Heroku docs](https://devcenter.heroku.com/articles/updating-heroku-postgres-databases). Another option is to clone the [wiki-heroku](https://github.com/Requarks/wiki-heroku/tree/beta) repository and edit the manifest to use the specific plan you need.
+- The deployment template will use the default PostgreSQL plan, which is the Hobby Dev (free) plan. You can upgrade to a larger plan afterwards as detailed in the [Heroku docs](https://devcenter.heroku.com/articles/updating-heroku-postgres-databases). Another option is to clone the [wiki-heroku](https://github.com/Requarks/wiki-heroku/tree/2.x) repository and edit the manifest to use the specific plan you need.
 - While the initial deployment is extremely quick and easy, **upgrading to a new version is not**. You'll need to push a new commit to your app git repo in order to trigger a new build. Unless you are comfortable with the Heroku workflow for deployments, you may want to look into alternative hosting solutions instead.
 - The free dyno plan (default) will "sleep" after 30 mins of inactivity. The first page load after such event will take several seconds to complete, as it must spin a new instance. Upgrade to a paid dyno plan to remove this limitation.
 - The database endpoint must be provided as `DATABASE_URL` environment variable to the app (default).
@@ -29,4 +29,4 @@ A workaround, which involves downgrading the database to PostgreSQL 10, is provi
 
 https://github.com/Requarks/wiki/issues/2949#issuecomment-773412440
 
-![](https://a.icons8.com/TgwPdfer/uNiaiQ/svg.svg){.align-abstopright}
+![](https://a.icons8.com/TgwPdfer/uNiaiQ/svg.svg){.align-abstopright}