chore(dotnet-tools.json): update dotnet-ef version to 7.0, which is default in Azure cloud shell

src/AdminSite/.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "dotnet-ef": {
-      "version": "6.0",
+      "version": "7.0",
       "commands": [
         "dotnet-ef"
       ]

src/CustomerSite/.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "dotnet-ef": {
-      "version": "6.0",
+      "version": "7.0",
       "commands": [
         "dotnet-ef"
       ]