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/maxItems.json

@@ -52,8 +52,8 @@
             {
               "code": "MAX_ITEMS_VIOLATED",
               "values": {
-                "count": "3",
-                "limit": "2"
+                "limit": "2",
+                "count": "3"
               },
               "details": {
                 "path": "",
@@ -115,8 +115,8 @@
             {
               "code": "MAX_ITEMS_VIOLATED",
               "values": {
-                "limit": "2",
-                "count": "3"
+                "count": "3",
+                "limit": "2"
               },
               "details": {
                 "path": "",
@@ -158,8 +158,8 @@
             {
               "code": "MAX_ITEMS_VIOLATED",
               "values": {
-                "limit": "2",
-                "count": "3"
+                "count": "3",
+                "limit": "2"
               },
               "details": {
                 "path": "",