Auto merge of #4714 - msizanoen1:remove-plugin, r=Manishearth

Remove clippy plugin

This PR removes the clippy plugin, which is already deprecated and is causing the `fmt_macros` not found error in rust-lang/rust#62558: rust-lang/rust#62558 (comment)

changelog: remove plugin interface

Author: bors

Cargo.toml

@@ -22,11 +22,6 @@ publish = false
 travis-ci = { repository = "rust-lang/rust-clippy" }
 appveyor = { repository = "rust-lang/rust-clippy" }
 
-[lib]
-name = "clippy"
-plugin = true
-test = false
-
 [[bin]]
 name = "cargo-clippy"
 test = false