👽 [#4795] Handle libmagic 5.46 behaviour

Validated with Sonny who's also using Arch - since libmagic 5.46 the
detected content type for these 'exotic' zip formats no longer reports
application/zip, but instead it returns application/octet-stream, or
otherwise said: it doesn't know those magic bytes (anymore).

Given the earlier patches, all we can do is allow these files to go
through.

Our Docker images are based on Debian bookworm, which ships libmagic
5.44. Debian unstable currently still has 5.44.

src/openforms/formio/api/validators.py

@@ -132,9 +132,10 @@ def __call__(self, value: UploadedFile) -> None:
             # which is deprecated but still we need to support it. Instead, the common
             # case for zip files is application/zip or application/zip-compressed
             # mimetype.
+            # libmagic 5.46+ doesn't detect application/zip anymore.
             case (
                 "application/zip-compressed" | "application/x-zip-compressed",
-                "application/zip",
+                "application/zip" | "application/octet-stream",
                 "zip",
             ):
                 return