fix(@schematics/angular): accept the project as a positional argument in refactor-jasmine-vitest

The karma-to-vitest migration suggests running
`ng g @schematics/angular:refactor-jasmine-vitest <project_name>`, but the
schematic only accepts the project through the `--project` option, so the
suggested command fails with `Unknown argument`.

Read the project from the first positional argument. When it is not provided,
the schematic still uses the only project of the workspace.

Author: MeAkib

packages/schematics/angular/refactor/jasmine-vitest/schema.json

@@ -16,9 +16,10 @@
     },
     "project": {
       "type": "string",
-      "description": "The name of the project where the tests should be refactored. If not specified, the CLI will determine the project from the current directory.",
+      "description": "The name of the project where the tests should be refactored. If not specified, the only project of the workspace is used.",
       "$default": {
-        "$source": "projectName"
+        "$source": "argv",
+        "index": 0
       }
     },
     "verbose": {