CI: keep download retry comment version-neutral

The truncated-download note named v4 as if it described the current
pin. Say it was seen on v4 so nobody reads the verify-and-retry steps
as a v4-only workaround and drops them.

Assisted-by: Claude Code:claude-opus-5-5

Author: claude

.github/actions/download-artifact/action.yml

@@ -18,8 +18,9 @@ inputs:
 runs:
   using: composite
   steps:
-    # download-artifact v4 can finish "successfully" with a truncated file:
-    # run 38059192473 attempt 1 logged "Starting download" and nothing more,
+    # download-artifact can finish "successfully" with a truncated file.
+    # Seen on v4; keep the check on newer majors too: run
+    # 38059192473 attempt 1 logged "Starting download" and nothing more,
     # then `zstd -d` failed with "Read error (39) : premature end" in the
     # next step and the leg went red. A merge-queue leg that does that
     # evicts the entry, so check the files and fetch them once more.