docs(plugin-legacy): fix typo

[Rotzbua]

Description

Seems to be a typo false should be true with option ignoreBrowserslistConfig.

Additional context

### `ignoreBrowserslistConfig`

- **Type:** `boolean`
- **Default:** `false`

  `@babel/preset-env` automatically detects [`browserslist` config sources](https://github.com/browserslist/browserslist#browserslist-):

  - `browserslist` field in `package.json`
  - `.browserslistrc` file in cwd.

  Set to `false` to ignore these sources.

Should be logical:

Set to true to ignore these sources.

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[bluwy]

Thanks!