Update dotnet-ef tool to match NuGet packages

We've switched to version 8.0.8 of the EF Core NuGet packages, so we
should update the dotnet-ef command-line tool to the same version.

.config/dotnet-tools.json

@@ -3,10 +3,10 @@
   "isRoot": true,
   "tools": {
     "dotnet-ef": {
-      "version": "8.0.5",
+      "version": "8.0.8",
       "commands": [
         "dotnet-ef"
       ]
     }
   }
-}
+}