chore(ci): unpin libc (#16044)

### What does this PR try to resolve?

[email protected]+ seems to have fixed it, we should be good to go and unpin:
[diff.rs/rustix/1.0.8/rustix/1.1.1/src%2Fbackend%2Flibc%2Fc.rs](https://diff.rs/rustix/1.0.8/rustix/1.1.1/src%2Fbackend%2Flibc%2Fc.rs)

Fixes #15919

### How to test and review this PR?

Same as <#15851>

> In rust-lang/rust, update the `src/tools/cargo` submodule accordingly,
and run
>
> ```
> cargo run --manifest-path src/ci/citool/Cargo.toml run-local
dist-loongarch64-musl
> ```
>
> With this downgrade it should compile.

I didn't run it locally though.

Author: Muscraft

.github/renovate.json5

@@ -8,8 +8,6 @@
   ignorePaths: [
     '**/tests/**',
   ],
-  // For why we ignore, see https://github.com/bytecodealliance/rustix/issues/1496
-  ignoreDeps: ['libc'],
   customManagers: [
     {
       customType: 'regex',