Drop `readme` and `resolver` fields from Cargo.toml

[LingMan]

The values they set don't differ from the defaults. From the manifest reference:

readme: "If no value is specified for this field, and a file named README.md, README.txt or README exists in the package root, then the name of that file will be used."

resolver: "The default is "2" if the root package specifies edition = "2021" or a newer edition."