btf: make btf::RelocationError private

BpfError::RelocationError type erases the inner error so no need to
export the type.

aya/src/obj/btf/mod.rs

@@ -6,5 +6,4 @@ mod types;
 
 pub use btf::*;
 pub(crate) use info::*;
-pub use relocation::RelocationError;
 pub(crate) use types::*;

aya/src/obj/btf/relocation.rs

@@ -18,7 +18,7 @@ use crate::{
 };
 
 #[derive(Error, Debug)]
-pub enum RelocationError {
+enum RelocationError {
     #[error(transparent)]
     IOError(#[from] io::Error),