MANIFEST.json.zst files are bigger than bz2 files

While looking into https://github.com/web-platform-tests/wpt/pull/33452 and trying to avoid the zstd binary as a dependency, I discovered that the MANIFEST.json.zst files are actually bigger than the bzip2 files we're uploading. In https://github.com/web-platform-tests/wpt/releases/tag/merge_pr_33467, we have:

MANIFEST.json.bz2: 2.08 MB (2180027 bytes)
MANIFEST.json.gz: 2.54 MB (2662852 bytes)
MANIFEST.json.zst: 2.09 MB (2190299 bytes)

In this case, zst is ~0.5% bigger than bz2.

bz2 and zst formats were introduced in https://github.com/web-platform-tests/wpt/pull/16083, but at the time zst was smaller:

MANIFEST.json.bz2: 1.94 MB
MANIFEST.json.gz: 2.37 MB
MANIFEST.json.zst: 1.86 MB

Since it requires an additional Python dependency we should reconsider if using zst is still really useful.

cc @gsnedders @jgraham

No file or test is named. Start by locating the release path that produces and uploads MANIFEST.json.bz2, MANIFEST.json.gz, and MANIFEST.json.zst, then compare its zstd dependency and compression choices. Done means a decided compression approach with the release artifacts and dependency requirements aligned.