Description of problem:
sha256 string is apparently prepended to sha1 checksums, leading to a "Unknown source reference(s)" error message from the osbuild-worker logs.

Version-Release number of selected component (if applicable):
osbuild-81-1.el8.noarch                                  
osbuild-composer-75-1.el8.x86_64 

How reproducible:
Always for the customer, not tested internally.

Steps to Reproduce:
Customer uses custom repos. Build works with Red Hat repos.

Actual results:
Jun 22 07:05:22 engage osbuild-worker[3678]: time="2023-06-22T07:05:22-04:00" level=info msg="Running job 'fe91b48e-4d60-4dfb-a814-3488c7311d9b' (osbuild)\n"
Jun 22 07:05:23 engage osbuild-worker[3720]: Traceback (most recent call last):
Jun 22 07:05:23 engage osbuild-worker[3720]:   File "/usr/bin/osbuild", line 11, in <module>
Jun 22 07:05:23 engage osbuild-worker[3720]:     load_entry_point('osbuild==81', 'console_scripts', 'osbuild')()
Jun 22 07:05:23 engage osbuild-worker[3720]:   File "/usr/lib/python3.6/site-packages/osbuild/main_cli.py", line 119, in osbuild_cli
Jun 22 07:05:23 engage osbuild-worker[3720]:     manifest = fmt.load(desc, index)
Jun 22 07:05:23 engage osbuild-worker[3720]:   File "/usr/lib/python3.6/site-packages/osbuild/formats/v2.py", line 369, in load
Jun 22 07:05:23 engage osbuild-worker[3720]:     load_pipeline(desc, index, manifest, source_refs)
Jun 22 07:05:23 engage osbuild-worker[3720]:   File "/usr/lib/python3.6/site-packages/osbuild/formats/v2.py", line 348, in load_pipeline
Jun 22 07:05:23 engage osbuild-worker[3720]:     load_stage(desc, index, pl, manifest, source_refs)
Jun 22 07:05:23 engage osbuild-worker[3720]:   File "/usr/lib/python3.6/site-packages/osbuild/formats/v2.py", line 317, in load_stage
Jun 22 07:05:23 engage osbuild-worker[3720]:     load_input(name, desc, index, stage, manifest, source_refs)
Jun 22 07:05:23 engage osbuild-worker[3720]:   File "/usr/lib/python3.6/site-packages/osbuild/formats/v2.py", line 273, in load_input
Jun 22 07:05:23 engage osbuild-worker[3720]:     raise ValueError(f"Unknown source reference(s) {unknown_refs}")
Jun 22 07:05:23 engage osbuild-worker[3720]: ValueError: Unknown source reference(s) {'sha256:sha1:8690e1630d166993982f2f70357f1a94b863a487', 'sha256:sha1:42affa70485aa6eff462c6bd0894f83b25380062', 'sha256:sha1:2442288093424d972f6034d27bae90da7eaf4c91', 'sha256:sha1:40778aac9da5bc14acad5f142cc5ab153e29f1c0', 'sha256:sha1:c828b451023a1adfc47b43337175509c6285a78d',