Update docs in buildpacks/r.py
@@ -26,7 +26,7 @@ class RBuildPack(PythonBuildPack):
If there is no `runtime.txt`, then the MRAN snapshot is set to latest
date that is guaranteed to exist across timezones.
- R packages are installed if specified either
+ Additional R packages are installed if specified either
- in a file `install.R`, that will be executed at build time,
and can be used for installing packages from both MRAN and GitHub
