Remove deprecated charts_repo_url inputs in doc (#137)

Signed-off-by: Kevin Park <krapi0314@gmail.com>

README.md

@@ -8,7 +8,7 @@ A GitHub action to turn a GitHub project into a self-hosted Helm chart repo, usi
 
 1. A GitHub repo containing a directory with your Helm charts (default is a folder named `/charts`, if you want to
    maintain your charts in a different directory, you must include a `charts_dir` input in the workflow).
-1. A GitHub branch called `gh-pages` to store the published charts. See `charts_repo_url` for alternatives.
+1. A GitHub branch called `gh-pages` to store the published charts.
 1. In your repo, go to Settings/Pages. Change the `Source` `Branch` to `gh-pages`.
 1. Create a workflow `.yml` file in your `.github/workflows` directory. An [example workflow](#example-workflow) is available below.
    For more information, reference the GitHub Help Documentation for [Creating a workflow file](https://help.github.com/en/articles/configuring-a-workflow#creating-a-workflow-file)