DashboardSchema: Remove old unused legacy props style and timepicker.enable (#73879)

* DashboardScheam: Remove old unused legacy props style and timepicker.enable

* Update

* fix test

devenv/dev-dashboards/datasource-testdata/bar-gauge-demo2.json

@@ -472,7 +472,6 @@
     }
   ],
   "schemaVersion": 21,
-  "style": "dark",
   "tags": ["gdev", "demo"],
   "templating": {
     "list": []

devenv/dev-dashboards/datasource-testdata/demo1.json

@@ -1077,7 +1077,6 @@
   ],
   "refresh": false,
   "schemaVersion": 18,
-  "style": "dark",
   "tags": ["gdev", "demo"],
   "templating": {
     "list": []

devenv/dev-dashboards/datasource-testdata/new_features_in_v62.json

@@ -1317,7 +1317,6 @@
   ],
   "refresh": "",
   "schemaVersion": 18,
-  "style": "dark",
   "tags": ["gdev", "demo"],
   "templating": {
     "list": []

devenv/dev-dashboards/datasource-testdata/new_features_in_v74.json

@@ -2165,7 +2165,6 @@
   ],
   "refresh": false,
   "schemaVersion": 27,
-  "style": "dark",
   "tags": [
     "gdev",
     "graph-ng",

devenv/dev-dashboards/datasource-testdata/new_features_in_v8.json

@@ -2814,7 +2814,6 @@
   ],
   "refresh": false,
   "schemaVersion": 33,
-  "style": "dark",
   "tags": [
     "gdev",
     "graph-ng",