chore(dashboard): Cleanup example dashboard filter scopes (#23260)

superset/examples/configs/dashboards/COVID_Vaccine_Dashboard.yaml

@@ -318,15 +318,15 @@ metadata:
     COUNT(*): "#D1C6BC"
   filter_scopes:
     "3965":
-      Country_Name:
+      country_name:
         scope:
           - ROOT_ID
         immune: []
-      Product_Category:
+      product_category:
         scope:
           - ROOT_ID
         immune: []
-      Clinical Stage:
+      clinical_stage:
         scope:
           - ROOT_ID
         immune: []

superset/examples/configs/dashboards/FCC_New_Coder_Survey_2018.yaml

@@ -717,7 +717,7 @@ metadata:
   color_scheme: supersetColors
   filter_scopes:
     '1387':
-      Ethnic Minority:
+      ethnic_minority:
         scope:
         - TAB-AsMaxdYL_t
         immune: []
@@ -725,7 +725,7 @@ metadata:
         scope:
         - ROOT_ID
         immune: []
-      Developer Type:
+      developer_type:
         scope:
         - ROOT_ID
         immune: []

superset/examples/configs/dashboards/Sales_Dashboard.yaml

@@ -386,12 +386,12 @@ metadata:
   refresh_frequency: 0
   default_filters: '{"671": {"__time_range": "No filter"}}'
   filter_scopes:
-    '671':
-      ProductLine:
+    "671":
+      product_line:
         scope:
         - TAB-4fthLQmdX
         immune: []
-      DealSize:
+      deal_size:
         scope:
         - ROOT_ID
         immune: []

superset/examples/configs/dashboards/Video_Game_Sales.yaml

@@ -370,16 +370,16 @@ metadata:
     "No filter"}}'
   color_scheme: supersetColors
   filter_scopes:
-    '3547':
-      Platform:
+    "3547":
+      platform:
         scope:
         - TAB-2_QXp8aNq
         immune: []
-      Genre:
+      genre:
         scope:
         - ROOT_ID
         immune: []
-      Publisher:
+      publisher:
         scope:
         - ROOT_ID
         immune: []