mononoke: do not read common bookmarks from commit sync config

Summary:
Our current megarepo configuration is in a bit of a mess:
1) We have LiveCommitSyncConfig, which fetches the latest version of configs
from configerator and should be used in all cases
2) However we still have an old commit that's stored in mononoke config. It
shouldn't really be used at all.

Unfortunately there are a few places where #2 is still used. This diff removes
one of them.

Reviewed By: ikostia

Differential Revision: D23845297

fbshipit-source-id: aa2d591223cc4b8fe5ef264147457fcb3d1faad7

Author: StanislavGlebik

eden/mononoke/commit_rewriting/mononoke_x_repo_sync_job/src/main.rs

@@ -415,14 +415,6 @@ async fn run(
     let (_, source_repo_config) = args::get_config_by_repoid(fb, &matches, source_repo_id)?;
     let (_, target_repo_config) = args::get_config_by_repoid(fb, &matches, target_repo_id)?;
 
-    let common_bookmarks: HashSet<_> = source_repo_config
-        .commit_sync_config
-        .clone()
-        .ok_or(format_err!("commit sync config not found!"))?
-        .common_pushrebase_bookmarks
-        .into_iter()
-        .collect();
-
     let logger = ctx.logger();
     let source_repo = args::open_repo_with_repo_id(fb, &logger, source_repo_id, &matches).compat();
     let target_repo = args::open_repo_with_repo_id(fb, &logger, target_repo_id, &matches).compat();
@@ -438,6 +430,12 @@ async fn run(
     let commit_sync_config =
         live_commit_sync_config.get_current_commit_sync_config(&ctx, source_repo.get_repoid())?;
 
+    let common_bookmarks: HashSet<_> = commit_sync_config
+        .common_pushrebase_bookmarks
+        .clone()
+        .into_iter()
+        .collect();
+
     let commit_syncer = commit_syncer_args
         .clone()
         .try_into_commit_syncer(&commit_sync_config)?;