ProductId: remove property

At both the top-level and in Item.Board.Motherboard schemas was a
required property: "ProductId".  This property has never been documented
in phosphor-dbus-interfaces and is only used in exactly 1 OEM IPMI
provider (and no where else)[1, 2].  Strip this unused property out.

Test Plan: entity-manager schema validators pass.  Search in code base
for usages.

[1]: https://github.com/openbmc/intel-ipmi-oem/blob/0fcc73f1cf8c486bb8079e68813c239c4cc41bbc/src/oemcommands.cpp#L2929
[2]: https://github.com/search?q=org%3Aopenbmc+%2F%28%3F-i%29ProductId%2F+-repo%3Aopenbmc%2Flinux+-repo%3Aopenbmc%2Fqemu&type=code

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I81f02c54aaee78e5d1c3b3e020437ebd3d7b4e3f
diff --git a/configurations/meta/minerva_cmm.json b/configurations/meta/minerva_cmm.json
index 21cadb8..822774f 100644
--- a/configurations/meta/minerva_cmm.json
+++ b/configurations/meta/minerva_cmm.json
@@ -260,9 +260,7 @@
         "xyz.openbmc_project.Inventory.Decorator.AssetTag": {
             "AssetTag": "$PRODUCT_ASSET_TAG"
         },
-        "xyz.openbmc_project.Inventory.Item.Board.Motherboard": {
-            "ProductId": 1
-        },
+        "xyz.openbmc_project.Inventory.Item.Board.Motherboard": {},
         "xyz.openbmc_project.Inventory.Item.NetworkInterface": {
             "MACAddress": "$CHASSIS_INFO_AM2"
         }