chore: remove the TestBox stubs that #3360 re-added after #3363 removed them

Third occurrence of the same slip, with a wrinkle worth recording.

PR #3363 untracked seven generated TestBox stubs and added the .gitignore entries that stop
them coming back. PR #3360 then merged on top and re-added all seven — its branch was cut from
2c98644, before the ignore existed, and it was committed with `git add -A` while the paths
were still untrackable-but-not-ignored. Merging the cleanup first and the older branch second
undid the cleanup.

The .gitignore is on develop now, so a branch cut from this point cannot repeat it. This
commit just finishes what #3363 started: seven removals, no other change.

Verified after committing that exactly one stub remains tracked — F952D54F…, which predates
all of this and is deliberately left alone.

The lesson is about ORDER, not just about `git add -A`: after merging a cleanup PR, every
already-open branch that predates it still carries the thing that was cleaned, and merging it
silently reverts the fix. Check the remaining branches for it before merging them, not after.

Signed-off-by: Peter Amiri <peter@alurium.com>

Author: bpamiri