Remove read-only flag from NTPServers

The NTPServers API no longer permits static assignment of
NTPServers. This is a result of adding the read-only flag to the
NTPServers D-Bus element.

The API needs to allow submitters to assign NTPServers. This entry
needs to allow read/write operations.

Tested:
After removing the read-only flag a Restclient PATCH request to the
NTPServers succeeds. Inspection of the systemd.network configuration
file confirms the values are propagated to the phosphor-network
receiver.

Change-Id: Ia2944738fe2bb9c5312207b1df21d8be9ddc5af2
Signed-off-by: Johnathan Mantey <johnathanx.mantey@intel.com>
diff --git a/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml b/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
index 096f5b5..e4bfffe 100644
--- a/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
+++ b/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
@@ -55,8 +55,6 @@
           - xyz.openbmc_project.Common.Error.InvalidArgument
     - name: NTPServers
       type: array[string]
-      flags:
-          - readonly
       description: >
           NTP servers that are currently in use on this interface.
           This includes both DHCP and static NTP server addresses.