config: Remove incorrect "after the container namespaces are created"

Not all hooks are run after creation.  In fact, there are currently no
postcreate hooks (prestart hooks are called "after the start operation
is called but before the user-specified program command is executed".

Fixing 28e8f68 (Hooks to linux,solaris and doc clarification,
2017-05-24, opencontainers#855), which pulled the broken line in from a Go comment
[1].

[1]: opencontainers#855 (comment)

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

config.md

@@ -365,7 +365,6 @@ Runtime implementations MAY support any valid values for platform-specific field
 ## <a name="configHooks" />Hooks
 
 Hooks allow for the configuration of custom actions related to the [lifecycle](runtime.md#lifecycle) of the container if supported by the platform.
-On Linux, they are run after the container namespaces are created.
 
 * **`hooks`** (object, OPTIONAL) MAY contain any of the following properties:
     * **`prestart`** (array of objects, OPTIONAL) is an array of [pre-start hooks](#prestart).