Removing feature directive tuple_indexing and if_let as both these features are added to Rust

While compiling rust, I am getting warning regarding tuple_indexing and if_let not required as added part of the Rust.   I have removed these directives.

    rust/rust/src/librustc_borrowck/lib.rs:19:40: 19:46 warning: feature has been added to Rust, directive not necessary
    rust/src/librustc_borrowck/lib.rs:19 #![feature(default_type_params, globs, if_let, import_shadowing, macro_rules, phase, quote)]
                                                                                                        ^~~~~~
    rust/src/librustc_borrowck/lib.rs:20:28: 20:42 warning: feature has been added to Rust, directive not necessary
    /rust/src/librustc_borrowck/lib.rs:20 #![feature(slicing_syntax, tuple_indexing, unsafe_destructor)]