[plugins.json] Add cocoapods-fix-xcframework-slice

[nakahira]

Please add the following entry to the plugins.json file:

{
  "gem": "cocoapods-fix-xcframework-slice",
  "name": "cocoapods-fix-xcframework-slice",
  "author": "nakahira",
  "url": "https://github.com/xuzhongping/cocoapods-fix-xcframework-slice",
  "description": "fix cocoapods-1.9.3 slice xcframework process"
}