testdata: drop unused uppercase SSH-*.hujson fixtures

The 39 SSH-*.hujson files in hscontrol/policy/v2/testdata/ssh_results/
were legacy hand-written "expected SSH rules" snippets superseded by
the lowercase tscap captures (ssh-*.hujson). The active loader in
TestSSHDataCompat globs ssh-*.hujson; filepath.Glob is case-sensitive
on Linux so the uppercase set was loaded by no test.

The duplication caused permanent dirty git state on case-insensitive
filesystems (APFS, NTFS) where only one of SSH-A1.hujson and
ssh-a1.hujson can physically exist in the working tree.

Add an assertion to TestSSHDataCompat that the loader picks up every
*.hujson under ssh_results/ so future fixture migrations cannot leave
stranded files behind.

Fixes #3240