Fix build. (#3739)

## Motivation

#3722 and
#3729 were merged
without rebasing, breaking the build.

## Proposal

Move `block_exporter_context` to the right `impl`.

## Test Plan

CI

## Release Plan

- Nothing to do / These changes follow the usual release cycle.

## Links

- [reviewer
checklist](https://github.com/linera-io/linera-protocol/blob/main/CONTRIBUTING.md#reviewer-checklist)

Author: afck

linera-storage/src/db_storage.rs

@@ -892,6 +892,15 @@ where
         }
         Ok(blob_ids)
     }
+
+    pub async fn block_exporter_context(
+        &self,
+        block_exporter_id: u32,
+    ) -> Result<ViewContext<u32, Store>, ViewError> {
+        let root_key = bcs::to_bytes(&BaseKey::BlockExporterState(block_exporter_id))?;
+        let store = self.store.clone_with_root_key(&root_key)?;
+        Ok(ViewContext::create_root_context(store, block_exporter_id).await?)
+    }
 }
 
 impl<Store> DbStorage<Store, WallClock>
@@ -915,15 +924,6 @@ where
         }
         Ok(chain_ids)
     }
-
-    pub async fn block_exporter_context(
-        &self,
-        block_exporter_id: u32,
-    ) -> Result<ViewContext<u32, Store>, ViewError> {
-        let root_key = bcs::to_bytes(&BaseKey::BlockExporterState(block_exporter_id))?;
-        let store = self.store.clone_with_root_key(&root_key)?;
-        Ok(ViewContext::create_root_context(store, block_exporter_id).await?)
-    }
 }
 
 #[cfg(with_testing)]