Allow generation of metrics.json simply by accessing the artifacts folder.

report_generator/vendor/README.md

@@ -3,18 +3,9 @@
 Copies of everything `report_generator` borrows from the monorepo, so the package can be lifted into
 a repository of its own.
 
-Nothing in here is edited. `sync.py` writes it, under the same import paths the monorepo uses:
-
-```
-python -m persistent_storage.report_generator.vendor.sync
-```
-
-Re-run it after changing anything it lists; the diff then shows what drifted. The copied packages
-are removed whole first, so dropping an entry from the list actually drops it from the tree.
-
-`__init__.py` decides whether these copies are used. It asks whether the real packages can be
-imported — not a flag, not an environment variable — so the same code runs in the monorepo and
-outside it, and the copies can never shadow the real packages while those are present.
+The files in here are committed with the standalone package. `__init__.py` puts
+these copies first on `sys.path`, so the package does not accidentally use an
+unrelated installed copy of one of these packages.
 
 ## What is copied, and what for