fix: skip installed packages

lib/yashchiki/specfile_storage_path.py

@@ -30,8 +30,8 @@ for rspec in data:
     
     for ss in maybe_to_be_fetched:
         # we could skip sources for already installed packages?
-        #if ss.installed:
-        #    continue
+        if ss.installed:
+            continue
         pkg = ss.package
         to_be_fetched.append(pkg)
         print(spack.mirror.mirror_archive_paths(pkg.fetcher, 'whatever').storage_path)