Fix feature enablement

Previously, `documented-macros` had `customise` erroneously enabled by default,
causing it to be enabled at all times, regardless of whether `customise` is on
or not on `documented`. This is now fixed.

documented-macros/Cargo.toml

@@ -24,4 +24,3 @@ documented = { path = "../lib" }
 
 [features]
 customise = ["dep:itertools", "dep:optfield", "dep:strum"]
-default = ["customise"]

documented-macros/src/config/derive.rs

@@ -39,6 +39,7 @@ impl DeriveConfig {
 
 // This is implemented instead of `syn::parse::Parse` because the options
 // can come from multiple attributes and therefore multiple `MetaList`s.
+#[cfg(feature = "customise")]
 impl TryFrom<Vec<ConfigOption>> for DeriveCustomisations {
     type Error = syn::Error;