test(jspg): rename items fixture to array and resolve unused HashMap warning

- Rename fixtures/items.json to fixtures/array.json to better reflect array testing constraints.
- Update reference paths in src/tests/fixtures.rs and across other fixture JSON files.
- Remove unused HashMap import in src/validator/rules/dict.rs to resolve the compiler warning.

fixtures/minItems.json

@@ -48,8 +48,8 @@
             {
               "code": "MIN_ITEMS_VIOLATED",
               "values": {
-                "count": "0",
-                "limit": "1"
+                "limit": "1",
+                "count": "0"
               },
               "details": {
                 "path": "",
@@ -108,8 +108,8 @@
             {
               "code": "MIN_ITEMS_VIOLATED",
               "values": {
-                "limit": "1",
-                "count": "0"
+                "count": "0",
+                "limit": "1"
               },
               "details": {
                 "path": "",