json: adjust definitions alias

JSON Schema suggests[1] using "$defs" rather than "definitions" as
the location for reusable definitions in a schema.  While, this
isn't strictly required, there is some implication that using it
lends to better schema validation error reporting[2].

Adjust all the schema files to use "$defs" rather than "definitions".

[1]: https://json-schema.org/understanding-json-schema/structuring#defs
[2]: https://github.com/orgs/json-schema-org/discussions/151

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4b23890950bd2ebb7a7de99fd911fb3c9e0a4dbd
diff --git a/schemas/ibm.json b/schemas/ibm.json
index c496652..dd3ec89 100644
--- a/schemas/ibm.json
+++ b/schemas/ibm.json
@@ -1,6 +1,6 @@
 {
     "$schema": "http://json-schema.org/draft-07/schema#",
-    "definitions": {
+    "$defs": {
         "IBMCFFPSConnector": {
             "title": "IBM Common Form Factor (CFF) Power Supply connectors",
             "description": "A schema associating an I2C endpoint and a GPIO for IBM CFF power supplies.  In the entity-manager detector-configuration-reactor architecture, the daemon that supports IBM CFFPS is both a detector and reactor.  It probes the endpoints described by this schema (reactor) and publishes the CFFPS FRU information (detector).",