fix: using docker registry instead of gcr (#318)

Author: pacostas

README.md

@@ -11,7 +11,7 @@ your CNB platform of choice offers.
 For example, with the `pack` CLI, use `--buildpack` as follows:
 ```bash
 pack build dotnet-with-buildpackless-builder \
---buildpack gcr.io/paketo-buildpacks/dotnet-core \
+--buildpack index.docker.io/paketobuildpacks/dotnet-core \
 --builder paketobuildpacks/builder-jammy-buildpackless-base:latest
 ```
 

smoke.json

@@ -1,3 +1,3 @@
 {
-  "procfile" :  "gcr.io/paketo-buildpacks/procfile"
+  "procfile" :  "index.docker.io/paketobuildpacks/procfile"
 }