Seems like apple/swift broke building for old release versions again

We use the following commands for building Swift Compiler on our internal CI:

    mkdir AppleLLVM
    cd AppleLLVM
   git clone https://github.com/apple/swift.git
cd swift
    utils/update-checkout --tag swift-5.4-RELEASE
    utils/update-checkout --clone
    utils/update-checkout --tag swift-5.4-RELEASE

to fetch Swift source code, which was working fine until recently, which now gives the following exceptions:

Traceback (most recent call last):
  File "utils/update-checkout", line 15, in <module>
    update_checkout.main()
  File "/Volumes/data/workspace/AppleLLVM/swift/utils/update_checkout/update_checkout/update_checkout.py", line 587, in main
    skip_repo_list)
  File "/Volumes/data/workspace/AppleLLVM/swift/utils/update_checkout/update_checkout/update_checkout.py", line 353, in obtain_all_additional_swift_sources
    obtain_additional_swift_sources, pool_args, args.n_processes)
  File "/Volumes/data/workspace/AppleLLVM/swift/utils/update_checkout/update_checkout/update_checkout.py", line 51, in run_parallel
    results = pool.map_async(func=fn, iterable=pool_args).get(999999)
  File "/Users/bkdevops/.pyenv/versions/2.7.16/lib/python2.7/multiprocessing/pool.py", line 572, in get
    raise self._value
Exception: ['git', '--git-dir', u'/Volumes/data/workspace/AppleLLVM/llvm-project/.git', '--work-tree', u'/Volumes/data/workspace/AppleLLVM/llvm-project', 'checko
ut', u'swift/main']
.....
======UPDATE FAILURES======

AppleLLVM/llvm-project failed (ret=1): ['git', 'checkout', u'swift/main']
error: pathspec 'swift/main' did not match any file(s) known to git

update-checkout failed, fix errors and try again

If my understanding is correct here, this is due to

swift/update-checkout-config.json at 3e4fab9bb6a56fc30d43e72eaff5b096cf160c55 · apple/swift · GitHub specifying to checkout llvm-project to swift/main, which no longer exists for some reason