Remove compiler-builtins from rustc-dep-of-std dependencies (#108)

Since [1], this will come automatically from `rustc-std-workspace-core`
and the crates.io dependency should no longer be specified.

[1]: rust-lang/rust#141993

Author: tgross35

Cargo.toml

@@ -16,15 +16,14 @@ members = ['crates/witx-bindgen', 'crates/wasi-ephemeral']
 
 [dependencies]
 # When built as part of libstd
-compiler_builtins = { version = "0.1", optional = true }
 core = { version = "1.0", optional = true, package = "rustc-std-workspace-core" }
 rustc-std-workspace-alloc = { version = "1.0", optional = true }
 
 [features]
 default = ["std"]
 std = []
 # Unstable feature to support being a libstd dependency
-rustc-dep-of-std = ["compiler_builtins", "core", "rustc-std-workspace-alloc"]
+rustc-dep-of-std = ["core", "rustc-std-workspace-alloc"]
 
 [badges]
 maintenance = { status = "experimental" }