<!-- Click "Preview" for a more readable version --

Please read and follow the instructions before submitting an issue:

- Read all our documentation, especially the [README](https://github.com/axios/axios/blob/master/README.md). It may contain information that helps you solve your issue.
- Ensure your issue isn't already [reported](https://github.com/axios/axios/issues?utf8=%E2%9C%93&q=is%3Aissue).
- If you aren't sure that the issue is caused by Axios or you just need help, please use [Stack Overflow](https://stackoverflow.com/questions/tagged/axios) or [our chat](https://gitter.im/mzabriskie/axios).
- If you're reporting a bug, ensure it isn't already fixed in the latest Axios version.
- Don't remove any title of the issue template, or it will be treated as invalid by the bot.

⚠️👆 Feel free to these instructions before submitting the issue 👆⚠️
-->

#### Describe the bug

`config.paramsSerializer.indexes = false` (default) adds indexes if an object is inside an array but it shouldn't.

#### To Reproduce

https://runkit.com/doits/634530f2d3a446000813ef73

```js
var axios = require("axios")

const req = await axios.get('https://www.example.com', { params: { a: [{ name: 'abc' }], b: ['x', 'y'] } })

console.log(req.request.path)

// => "/?a[0][name]=abc&b[]=x&b[]=y"
```

#### Expected behavior

No `a[0]` but `a[]`:

```js
// => "/?a[][name]=abc&b[]=x&b[]=y"
```

#### Environment
 - Axios Version 1.1.2

#### Additional context/Screenshots

None

index.d.ts
s: FormDataVisitorHelpers
  ): boolean;
}
export interface SerializerOptions {
  visitor?: SerializerVisitor;
  dots?: boolean;
  metaTokens?: boolean;
  indexes?: boolean | null;
}
export interface FormSerializerOptions extends SerializerOptions {
}
export interface ParamEncoder {
  (value: any, defaultEncoder: (value: any) => any): any;
}
export interface CustomParamsSerializer {
  (params: object, options?: ParamsSerializerOptions): string;
}
export interface ParamsSerializerOptions extends SerializerOptions {
  encode?: ParamEncoder;
  serialize?: CustomParamsSerializer;
}
type MaxUploadRate = number;
type MaxDownloadRate = number;
export interface AxiosProgressEvent {
  loaded: number;
  total?: number;
  progress?: number;
  bytes: number;
  rate?: number;
  estimated?: number;
  upload?: boolean;
  download?: boolean;
}
type Milliseconds = number;
export interface AxiosRequestConfig<D = any> {
  url?: string;
  method?: Method | string;
  baseURL?: string;
  transformRequest?: AxiosRequestTransformer | AxiosRequestTransformer[];
  transformResponse?: AxiosResponseTransformer | AxiosResponseTransformer[];
  headers?: RawAxiosRequestHeaders;
  params?: any;
  paramsSerializer?: ParamsSerializerOptions;
  data?: D;
  timeout?: Milliseconds;
  timeoutErrorMessage?: string;
  withCredentials?: boolean;
  adapter?: AxiosAdapter;
  auth?: AxiosBasicCredentials;
  responseType?: ResponseType;
  responseEncoding?: responseEncoding | string;
  xsrfCookieName?: string;
  xsrfHeaderName?: string;
  onUploadProgress?: (progressEvent: AxiosProgressEvent) => void;
  onDownloadProgress?: (progressEvent: AxiosProgressEvent) => void;
  maxContentLength?: number;
  validateStatus?: ((status: number) => boolean) | null;
  maxBodyLength?: number;
  maxRedirects?: number;
  maxRate?: number | [MaxUploadRate, MaxDownloadRate];
  beforeRedirect?: (options: Record<string, any>, responseDetails: {headers: Record<string, string>}) => void;
  socketPath?: string | null;
  httpAgent?: an