Drop "one or more" from index description, follow up #644

Signed-off-by: Lei Jitang <[email protected]>

Author: coolljt0725

media-types.md

@@ -63,6 +63,6 @@ The following figure shows how the above media types reference each other:
 ![](img/media-types.png)
 
 [Descriptors](descriptor.md) are used for all references.
-The image-index being a "fat manifest" references one or more image manifests per target platform. An image manifest references exactly one target configuration and possibly many layers.
+The image-index being a "fat manifest" references a list of image manifests per target platform. An image manifest references exactly one target configuration and possibly many layers.
 
 [rfc1952]: https://tools.ietf.org/html/rfc1952

spec.md

@@ -36,7 +36,7 @@ An implementation is compliant if it satisfies all the MUST, REQUIRED, and SHALL
 
 At a high level the image manifest contains metadata about the contents and dependencies of the image including the content-addressable identity of one or more [filesystem layer changeset](layer.md) archives that will be unpacked to make up the final runnable filesystem.
 The image configuration includes information such as application arguments, environments, etc.
-The image index is a higher-level manifest which points to one or more manifests and descriptors.
+The image index is a higher-level manifest which points to a list of manifests and descriptors.
 Typically, these manifests may provide different implementations of the image, possibly varying by platform or other attributes.
 
 ![](img/build-diagram.png)