Error: not supported

After successful ember-cli-update to 3.28.3

```
ember -v
ember-cli: 3.28.3
node: 12.16.1
os: darwin x64
```

`--run-codemods` fails with `Error: Not supported`

```
DEBUG=ember-cli-update,boilerplate-update,git-diff-apply ember-cli-update --run-codemods
? Which blueprint would you like to run codemods for? ember-cli
Error: Not supported
at getApplicableCodemods (/Users/bryan/.config/yarn/global/node_modules/boilerplate-update/src/get-applicable-codemods.js:19:32)
at async getAndPromptCodemods (/Users/bryan/.config/yarn/global/node_modules/boilerplate-update/src/get-and-prompt-codemods.js:12:18)
at async promptAndRunCodemods (/Users/bryan/.config/yarn/global/node_modules/boilerplate-update/src/prompt-and-run-codemods.js:13:18)
at async codemods (/Users/bryan/.config/yarn/global/node_modules/ember-cli-update/src/codemods.js:80:10)
at async Object.handler (/Users/bryan/.config/yarn/global/node_modules/ember-cli-update/bin/commands/default.js:42:19)
```

Reproduce the failure with ember-cli-update --run-codemods using the versions shown. Start in boilerplate-update/src/get-applicable-codemods.js and follow the call from ember-cli-update/src/codemods.js; determine why the ember-cli blueprint is rejected, then verify the command completes or reports applicable codemods without the error.

Written by the indexing model from the issue text.