Update toolchain, get rid of the std-features hack

The `compiler-builtins-mangled-names` thingie¹ is no longer needed,
since `compiler_builtins` has been improved to avoid pulling the
problematic functions:

- rust-lang/compiler-builtins#462
- rust-lang/compiler-builtins#466
- rust-lang/rust#97435

¹ rust-lang/rust#82242

Author: Patryk27

.cargo/config.toml

@@ -36,7 +36,6 @@
 
 [unstable]
 build-std = ["core"]
-build-std-features = ["compiler-builtins-mangled-names"]
 {%- comment %}
 # vim: ft=toml.jinja2
 {% endcomment %}

rust-toolchain.toml

@@ -1,4 +1,4 @@
 [toolchain]
-channel = "nightly-2022-05-10"
+channel = "nightly-2022-06-13"
 components = ["rust-src"]
 profile = "minimal"