Update schema pack to 2021.4

Update the script to point to 2021.4.

Tested: built for evb-ast2500, ran Redfish Service Validator:
                             BASE    2021.4
metadataNamespaces:          2330      2388
pass:                        3239      3249
passAction:                     8         8
passGet:                      120       121
passRedfishUri:               114       115
skipNoSchema:                   3         3
skipOptional:                2180      2184
unverifiedAdditional.complex:   2         0
warnDeprecated:               315       315
warningPresent:                12        11
Validation has:         succeeded succeeded

Saw new schemas:
curl -k https://$bmc/redfish/v1/JsonSchemas/Manager/Manager.json
...
    "title": "#Manager.v1_14_0.Manager"
}

Signed-off-by: Sui Chen <suichen@google.com>
Change-Id: I6560ec010362df28e264d80452059b534b3f89ba
diff --git a/static/redfish/v1/JsonSchemas/VirtualMedia/VirtualMedia.json b/static/redfish/v1/JsonSchemas/VirtualMedia/VirtualMedia.json
index e853bf0..212266c 100644
--- a/static/redfish/v1/JsonSchemas/VirtualMedia/VirtualMedia.json
+++ b/static/redfish/v1/JsonSchemas/VirtualMedia/VirtualMedia.json
@@ -1,5 +1,5 @@
 {
-    "$id": "http://redfish.dmtf.org/schemas/v1/VirtualMedia.v1_5_0.json",
+    "$id": "http://redfish.dmtf.org/schemas/v1/VirtualMedia.v1_5_1.json",
     "$ref": "#/definitions/VirtualMedia",
     "$schema": "http://redfish.dmtf.org/schemas/v1/redfish-schema-v1.json",
     "copyright": "Copyright 2014-2021 DMTF. For the full DMTF copyright policy, see http://www.dmtf.org/about/policies/copyright",
@@ -413,7 +413,7 @@
                 },
                 "VerifyCertificate": {
                     "description": "An indication of whether the service will verify the certificate of the server referenced by the Image property prior to completing the remote media connection.",
-                    "longDescription": "This property shall indicate whether whether the service will verify the certificate of the server referenced by the Image property prior to completing the remote media connection.",
+                    "longDescription": "This property shall indicate whether whether the service will verify the certificate of the server referenced by the Image property prior to completing the remote media connection.  If this property is not supported by the service, it shall be assumed to be `false`.  This property should default to `false` in order to maintain compatibility with older clients.",
                     "readonly": false,
                     "type": [
                         "boolean",
@@ -442,5 +442,5 @@
     },
     "owningEntity": "DMTF",
     "release": "2021.2",
-    "title": "#VirtualMedia.v1_5_0.VirtualMedia"
+    "title": "#VirtualMedia.v1_5_1.VirtualMedia"
 }
\ No newline at end of file