Fix ogg vorbis files with a cover art not being correctly processed

[ClearlyClaire]

Paperclip runs files through a “spoof detector” to figure out whether they correspond to their advertised content-type.

In #14184, we have overridden part of that detection because it relied on the file utility which returns application/octet-stream for some mp3 files, and used MimeMagic instead.

However, MimeMagic detects Ogg Vorbis files with a cover art as video/ogg, while file correctly detects it as audio/ogg. This causes a mismatch when the file has an .oga extension, which is explicitly audio/ogg.

Furthermore, this leads to Ogg Vorbis files submitted with the .ogg and a cover art to not be correctly processed, failing to extract a thumbnail and converting them to .mp3. This is because the first validation passes interpreting it as a video/ogg file while our code later constructs a .oga extension based on the correctly detected audio/ogg, causing the actual processing to be skipped because of the mismatch.

This PR changes the detector to allow the validation to pass if it matches either FileMagic or file's output.