schema/defs-linux: Drop 'Capability' type

The current "For example, valid values for Linux..." wording in
config.md does not seem strong enough to support this condition,
especially since the spec makes no claims about what valid
capabilities are for non-Linux OSes.  And process.capabilities has
been nominally legal for non-Linux OSes since 718f9f3 (minor
narrative cleanup regarding config compatibility, 2017-01-30, opencontainers#673).

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

Author: wking

schema/config-schema.json

@@ -141,35 +141,35 @@
                             "id": "https://opencontainers.org/schema/bundle/process/linux/capabilities/bounding",
                             "type": "array",
                             "items": {
-                                "$ref": "defs-linux.json#/definitions/Capability"
+                                "type": "string"
                             }
                         },
                         "permitted": {
                             "id": "https://opencontainers.org/schema/bundle/process/linux/capabilities/permitted",
                             "type": "array",
                             "items": {
-                                "$ref": "defs-linux.json#/definitions/Capability"
+                                "type": "string"
                             }
                         },
                         "effective": {
                             "id": "https://opencontainers.org/schema/bundle/process/linux/capabilities/effective",
                             "type": "array",
                             "items": {
-                                "$ref": "defs-linux.json#/definitions/Capability"
+                                "type": "string"
                             }
                         },
                         "inheritable": {
                             "id": "https://opencontainers.org/schema/bundle/process/linux/capabilities/inheritable",
                             "type": "array",
                             "items": {
-                                "$ref": "defs-linux.json#/definitions/Capability"
+                                "type": "string"
                             }
                         },
                         "ambient": {
                             "id": "https://opencontainers.org/schema/bundle/process/linux/capabilities/ambient",
                             "type": "array",
                             "items": {
-                                "$ref": "defs-linux.json#/definitions/Capability"
+                                "type": "string"
                             }
                         }
                     }

schema/defs-linux.json

@@ -82,11 +82,6 @@
                 }
             }
         },
-        "Capability": {
-            "description": "Linux process capabilities",
-            "type": "string",
-            "pattern": "^CAP_([A-Z]|_)+$"
-        },
         "Major": {
             "description": "major device number",
             "$ref": "defs.json#/definitions/int64"