Revert "expose try_operation_with_failover publicly"

This reverts commit 7d48e5a.

Author: 0xNeshi

src/robust_provider/provider.rs

@@ -29,7 +29,7 @@ pub enum Error {
 
 /// Low-level error related to RPC calls and failover logic.
 #[derive(Error, Debug)]
-pub enum CoreError {
+pub(crate) enum CoreError {
     #[error("Operation timed out")]
     Timeout,
     #[error("RPC call failed after exhausting all retry attempts: {0}")]
@@ -343,7 +343,7 @@ impl<N: Network> RobustProvider<N> {
     ///   returned by the last provider attempted on the last retry.
     /// * [`CoreError::Timeout`] - if the overall operation timeout elapses (i.e. exceeds
     ///   `call_timeout`).
-    pub async fn try_operation_with_failover<T: Debug, F, Fut>(
+    pub(crate) async fn try_operation_with_failover<T: Debug, F, Fut>(
         &self,
         operation: F,
         require_pubsub: bool,