config-linux: Fix 'file' POSIX link

This was broken by f9dc90b (make link usage consistent across the
specification, 2017-02-09, opencontainers#687), which updated the link label, but
not this link.  Now that the link label matches the link text, we can
use the implicit link name shortcut [1].

[1]: https://daringfireball.net/projects/markdown/syntax#link

Signed-off-by: W. Trevor King <wking@tremily.us>

config-linux.md

@@ -114,7 +114,7 @@ Each entry has the following structure:
 * **`type`** *(string, REQUIRED)* - type of device: `c`, `b`, `u` or `p`.
   More info in [mknod(1)][mknod.1].
 * **`path`** *(string, REQUIRED)* - full path to device inside container.
-  If a [file][file.1] already exists at `path` that does not match the requested device, the runtime MUST generate an error.
+  If a [file][] already exists at `path` that does not match the requested device, the runtime MUST generate an error.
 * **`major, minor`** *(int64, REQUIRED unless `type` is `p`)* - [major, minor numbers][devices] for the device.
 * **`fileMode`** *(uint32, OPTIONAL)* - file mode for the device.
   You can also control access to devices [with cgroups](#device-whitelist).