Remove the feature flag for NaN boxing now that were closer in perf

cli/Cargo.toml

@@ -28,7 +28,6 @@ dhat = { workspace = true, optional = true }
 [features]
 default = ["boa_engine/annex-b", "boa_engine/experimental", "boa_engine/intl_bundled"]
 dhat = ["dep:dhat"]
-nan-box-jsvalue = ["boa_engine/nan-box-jsvalue"]
 
 [target.x86_64-unknown-linux-gnu.dependencies]
 jemallocator.workspace = true

core/engine/Cargo.toml

@@ -15,7 +15,6 @@ rust-version.workspace = true
 profiler = ["boa_profiler/profiler"]
 deser = ["boa_interner/serde", "boa_ast/serde"]
 either = ["dep:either"]
-nan-box-jsvalue = []
 
 # Enables the `Intl` builtin object and bundles a default ICU4X data provider.
 # Prefer this over `intl` if you just want to enable `Intl` without dealing with the

core/engine/src/value/inner.rs

@@ -1,18 +1,3 @@
 //! Module implementing the operations for the inner value of a `[super::JsValue]`.
-//!
-//! The `[InnerValue]` type is an opaque type that can be either an enum of possible
-//! JavaScript value types, or a 64-bits float that represents a NaN-boxed JavaScript
-//! value, depending on feature flags. By default, the behaviour is to use the
-//! enumeration.
-
-#[cfg(feature = "nan-box-jsvalue")]
 mod nan_boxed;
-
-#[cfg(feature = "nan-box-jsvalue")]
 pub(crate) use nan_boxed::NanBoxedValue as InnerValue;
-
-#[cfg(not(feature = "nan-box-jsvalue"))]
-mod enum_value;
-
-#[cfg(not(feature = "nan-box-jsvalue"))]
-pub(crate) use enum_value::EnumBasedValue as InnerValue;