Types of version 5.0.0 still allow `proxy` to be an object

[levrik]

Bug report

Actual Behavior

The TS typings still allow an object to be passed to the proxy option while it crashes at runtime.

Expected Behavior

The TS typings should be updated to reflect the API changes.

Please paste the results of npx webpack-cli info here, and mention other relevant information

System:
  OS: macOS 13.6.4
  CPU: (8) arm64 Apple M1 Pro
  Memory: 54.72 MB / 16.00 GB
Binaries:
  Node: 18.19.0 - /opt/homebrew/opt/node@18/bin/node
  Yarn: 1.22.19 - /opt/homebrew/bin/yarn
  npm: 10.2.3 - /opt/homebrew/opt/node@18/bin/npm
Browsers:
  Safari: 17.3.1
Packages:
  babel-loader: 9.1.3 => 9.1.3 
  copy-webpack-plugin: 12.0.2 => 12.0.2 
  fork-ts-checker-webpack-plugin: 9.0.2 => 9.0.2 
  html-webpack-plugin: 5.6.0 => 5.6.0 
  source-map-loader: 5.0.0 => 5.0.0 
  webpack: 5.90.3 => 5.90.3 
  webpack-cli: 5.1.4 => 5.1.4 
  webpack-dev-server: 5.0.2 => 5.0.2