Fix terminal profile schema to allow null in keybinding id (#19332)

Fixes the terminal profile jsonschema to allow for null in the id. This
is to match the current implementation when disabling a built in default
keybind.

(cherry picked from commit eb16eb26ab)
Service-Card-Id: PVTI_lADOAF3p4s4BBcTlzgemwL0
Service-Version: 1.24

doc/cascadia/profiles.schema.json

@@ -2302,8 +2302,15 @@
       "additionalProperties": false,
       "properties": {
         "id": {
-          "description": "The ID of the command this keybinding should execute.",
-          "type": "string"
+          "description": "The ID of the command this keybinding should execute (or null to disable a default).",
+          "oneOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ]
         },
         "keys": {
           "description": "Defines the key combinations used to call the command. It must be composed of...\n -any number of modifiers (ctrl/alt/shift)\n -a non-modifier key",