Replace el.toml with manifest.el throughout — El manifests are El, not TOML

crates/el-services/src/binding/mod.rs

@@ -1,7 +1,7 @@
 //! Service binding implementations.
 //!
 //! Each binding protocol implements the `Binding` trait.
-//! The proxy uses whatever binding is configured in `el.toml`.
+//! The proxy uses whatever binding is configured in `manifest.el`.
 
 pub mod direct;
 pub mod grpc;