docs: Add guide to remove untranslated field after translation

Author: roeniss

docs/translations.md

@@ -13,6 +13,7 @@ If there's not, then today is your day to lead this effort! Here's how to start:
 1. Create a new branch for your translation work e.g. `es`.
 1. Copy `_data/locales/en.yml` to your target language file e.g. `_data/locales/es.yml` and translate all the strings.
 1. Create a new directory in `_articles/` for your language e.g. `_articles/es/`, copy each guide from `_articles/` into that folder and translate the content in each guide, except for the field names in the front matter between the `---`s at the top of each file, e.g., `title:` should remain unchanged.
+1. Remove the untranslated field.
 1. Copy `index.html` to your target language index file e.g. `[_articles/es/index.html](https://github.com/github/opensource.guide/blob/HEAD/_articles/es/index.html)` and update the `lang:` and add the `permalink:` fields. Example: `lang: es` and `permalink: /es/`. All other fields' values must remain unchanged.
 1. Run `script/test` and make sure there are no failures with your translation files. Note that you may need to fix broken links.
 1. Send a pull request. (You may send a pull request before all steps above are complete: e.g., you may want to ask for help with translations, or getting tests to pass. However, your pull request will not be merged until all steps above are complete.)