Remove `rustc_driver::set_sigpipe_handler()`

Its usage was removed in 5e624bf4ba and 093b075d32, so we do not need to
keep it around any longer. According to [preliminary
input](https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Find.20.60rustc_driver.60.20dependent.20projects.3F/near/304490764),
we do not need to worry about any deprecation cycle for this API and can
just straight up remove it.

Migration instructions for remaining clients
--------------------------------------------

Change from

```rust

extern crate rustc_driver;

fn main() {
    rustc_driver::set_sigpipe_handler();
    // ...
```

to

```rust

fn main() {
    // ...
```

0 files changed, 0 insertions, 0 deletions