config: Fix broken JSON in Windows mount example
config: Fix broken JSON in Windows mount example

The 'key: value' syntax is for objects, but 'mounts' is an array.

Signed-off-by: W. Trevor King <f75897670c17327c42ab201733fb8a81ff9f4c34@tremily.us>

wking/opencontainer-specs,hqhq/specs,laijs/specs,hqhq/runtime-spec,opencontainers/runtime-spec,wking/opencontainer-runtime-spec,opencontainers/specs