pageserver: silence shard resolution warning (#12685)

## Problem

We drive the get page requests that have started processing to
completion. So in the case when the compute received a reconfiguration
request and the old connection has a request procesing on the
pageserver, we are going to issue the warning.

I spot checked a few instances of the warning and in all cases the
compute was already connected to the correct pageserver.

## Summary of Changes

Downgrade to INFO. It would be nice to somehow figure out if the
connection has been terminated in the meantime, but the terminate libpq
message is still in the pipe while we're doing the shard resolution.

Closes LKB-2381

pageserver/src/tenant/timeline/handle.rs

@@ -362,7 +362,7 @@ impl<T: Types> Cache<T> {
                         tokio::time::sleep(RETRY_BACKOFF).await;
                         continue;
                     } else {
-                        tracing::warn!(
+                        tracing::info!(
                             "Failed to resolve tenant shard after {} attempts: {:?}",
                             GET_MAX_RETRIES,
                             e