annotations: addressing comments

From: opencontainers#658 (comment)

* Source is not just to binaries.
* the strings already say URL, so it's redundant
* git:// is a valid URL as well

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

annotations.md

@@ -19,9 +19,9 @@ This property contains arbitrary metadata.
 This specification defines the following annotation keys, intended for but not limited to [image index](image-index.md) and image [manifest](manifest.md) authors:
 * **org.opencontainers.image.created** date on which the image was built (string, date-time as defined by [RFC 3339](https://tools.ietf.org/html/rfc3339#section-5.6)).
 * **org.opencontainers.image.authors** contact details of the people or organization responsible for the image (freeform string)
-* **org.opencontainers.image.homepage** URL to find more information on the image (string, a URL with scheme HTTP or HTTPS)
-* **org.opencontainers.image.documentation** URL to get documentation on the image (string, a URL with scheme HTTP or HTTPS)
-* **org.opencontainers.image.source** URL to get source code for the binary files in the image (string, a URL with scheme HTTP or HTTPS)
+* **org.opencontainers.image.homepage** URL to find more information on the image (string)
+* **org.opencontainers.image.documentation** URL to get documentation on the image (string)
+* **org.opencontainers.image.source** URL to get source code for the image-build (string)
 * **org.opencontainers.image.version** [Semantic versioning-compatible](http://semver.org/) version of the packaged software.
 * **org.opencontainers.image.revision** Source control revision identifier for packaged software.
 * **org.opencontainers.image.vendor** Name of the distributing entity, organization or individual.