Revert "Delete stale package_config.json in gclient sync hook (#57195)"

This reverts commit 2f6643235edc0beeb69e079d867d7581c5c6a6e9.

tools/pub_get_offline.py

diff --git a/tools/pub_get_offline.py b/tools/pub_get_offline.py
index 154c08e..2bf6b8a 100644
--- a/tools/pub_get_offline.py
+++ b/tools/pub_get_offline.py
@@ -127,17 +127,6 @@
   return unlisted
 
 
-def delete_config_files():
-  # Find all package_config.json that are not under version control.
-  gitcmd = ['git', 'ls-files', '-o', '**/.dart_tool/package_config.json']
-  files_to_delete = subprocess.check_output(
-      gitcmd, cwd=ENGINE_DIR, stderr=subprocess.STDOUT, text=True
-  ).splitlines()
-  for file in files_to_delete:
-    print('Deleting %s...' % file)
-    os.remove(os.path.join(ENGINE_DIR, file))
-
-
 def main():
   # Intentionally use the Dart SDK prebuilt instead of the Flutter prebuilt
   # (i.e. prebuilts/{platform}/dart-sdk/bin/dart) because the script has to run
@@ -146,10 +135,6 @@
       SRC_ROOT, 'flutter', 'third_party', 'dart', 'tools', 'sdks', 'dart-sdk', 'bin'
   )
 
-  # Delete all package_config.json files. These may be stale.
-  # Required ones will be regenerated fresh below.
-  delete_config_files()
-
   # Ensure all relevant packages are listed in ALL_PACKAGES.
   unlisted = find_unlisted_packages()
   if len(unlisted) > 0: