Remove incorrect duplicate phrase from build.md
A phrase from the "Text files" section in build.md was incorrectly duplicated under the "Tarball contexts" section.
@@ -112,9 +112,6 @@ Build Syntax Suffix | Commit Used | Build Context Used
If you pass an URL to a remote tarball, the URL itself is sent to the daemon:
-Instead of specifying a context, you can pass a single Dockerfile in the `URL`
-or pipe the file in via `STDIN`. To pipe a Dockerfile from `STDIN`:
-
```bash
$ docker build http://server/context.tar.gz
```
