Remove unnecessary imports from documentation

Author: krishna-veerareddy

CONTRIBUTING.md

@@ -110,7 +110,7 @@ It's worth noting that the majority of `clippy_lints/src/lib.rs` is autogenerate
 ```rust
 // ./clippy_lints/src/else_if_without_else.rs
 
-use rustc::lint::{EarlyLintPass, LintArray, LintPass};
+use rustc_lint::{EarlyLintPass, EarlyContext};
 
 // ...
 

doc/adding_lints.md

@@ -138,7 +138,7 @@ at `clippy_lints/src/foo_functions.rs`. That's the crate where all the
 lint code is. This file has already imported some initial things we will need:
 
 ```rust
-use rustc::lint::{LintArray, LintPass, EarlyLintPass, EarlyContext};
+use rustc_lint::{EarlyLintPass, EarlyContext};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use syntax::ast::*;
 ```