fix: spec_error is used by try_from derive (#3915)

The `try_from` field attribute in `FromRow` uses `__spec_error` to generate a column decode error. The `spec_error` is currently gated behind the macros feature flag only, but should also be available when using only `derive`.

Author: saiintbrisson

src/lib.rs

@@ -101,7 +101,7 @@ mod macros;
 #[doc(hidden)]
 pub mod ty_match;
 
-#[cfg(feature = "macros")]
+#[cfg(any(feature = "derive", feature = "macros"))]
 #[doc(hidden)]
 pub mod spec_error;