use unique $id in optional tests, too

Author: gregsdennis

tests/draft-next/optional/dynamicRef.json

@@ -3,7 +3,7 @@
       "description": "$dynamicRef skips over intermediate resources - pointer reference across resource boundary",
       "schema": {
           "$schema": "https://json-schema.org/draft/next/schema",
-          "$id": "https://example.com/foo",
+          "$id": "https://test.json-schema.org/dynamic-ref-skips-intermediate-resource/optional/main",
           "type": "object",
           "properties": {
               "bar-item": {
@@ -12,7 +12,7 @@
           },
           "$defs": {
               "bar": {
-                  "$id": "https://example.com/bar",
+                  "$id": "bar",
                   "type": "array",
                   "items": {
                       "$ref": "item"

tests/draft2020-12/optional/dynamicRef.json

@@ -3,16 +3,16 @@
       "description": "$dynamicRef skips over intermediate resources - pointer reference across resource boundary",
       "schema": {
         "$schema": "https://json-schema.org/draft/2020-12/schema",
-        "$id": "https://example.com/foo",
-          "type": "object",
+        "$id": "https://test.json-schema.org/dynamic-ref-skips-intermediate-resource/main",
+        "type": "object",
           "properties": {
               "bar-item": {
                   "$ref": "bar#/$defs/item"
               }
           },
           "$defs": {
               "bar": {
-                  "$id": "https://example.com/bar",
+                  "$id": "bar",
                   "type": "array",
                   "items": {
                       "$ref": "item"