Fix `KeyError` when running `add_miniforge.py`

I was attempting to run the script to generate build files for new
versions, but it failed because version `23.1.0-4`[^1] contained a
malformed `.sha256` file.[^2] I looked at the miniforge repo's script
`releases.py`[^3] and copied the logic about which release artifacts
should be skipped when generating a list of downloads.

[^1]: https://github.com/conda-forge/miniforge/releases/tag/23.1.0-4
[^2]: https://github.com/conda-forge/miniforge/releases/download/23.1.0-4/Miniforge3-uninstaller-patch-Windows-x86_64.exe.sha256
[^3]: a15762906b/docs/releases.py (L35-L36)

plugins/python-build/scripts/add_miniforge.py

@@ -71,8 +71,9 @@ def supported(filename):
     return ('pypy' not in filename) and ('Windows' not in filename)
 
 def add_version(release):
+    tag_name = release['tag_name']
     download_urls = { f['name']: f['browser_download_url'] for f in release['assets'] }
-    shas = dict([download_sha(url) for (name, url) in download_urls.items() if name.endswith('.sha256')])
+    shas = dict([download_sha(url) for (name, url) in download_urls.items() if name.endswith('.sha256') and tag_name in name])
     specs = [create_spec(filename, sha, download_urls[filename]) for (filename, sha) in shas.items() if supported(filename)]
 
     for distribution in DISTRIBUTIONS: