Remove all //blimp code.

blimp/docs/markdown.md

-# How to use Markdown
-
-Markdown is a lightweight markup language which can be easily converted to
-HTML.
-
-## Gitiles reference guide
-
-For the full reference guide for the version of Markdown used to render Chromium
-pages, see the [reference for Gitiles Markdown][gtref].
-
-## Google style guide
-
-Be sure to read the
-[Google style guide for Markdown](https://github.com/google/styleguide/blob/gh-pages/docguide/style.md).
-
-## Local preview of changes
-
-To see how the pages you edit will look, run the following command from your
-Chromium checkout (`src/` directory) to start up a server on
-http://localhost:8080/:
-
-```bash
-python tools/md_browser/md_browser.py
-```
-
-You can then navigate to http://localhost:8080/blimp/README.md
-in your browser to see the result locally. Just refresh the page after saving
-a `*.md` file to see an updated result.
-
-[gtref]: https://gerrit.googlesource.com/gitiles/+/master/Documentation/markdown.md