test: re-cite retired-mechanism comments in surviving carriers

The migrate-and-retire audit left the surviving carriers as the only
files still describing the retired combined.ww amalgamator as live:
m2wwi/m3sep headers claimed .wwi was dead code, four byteid carriers
carried dead cleanup of never-written .combined.ww intermediates, and
sepbuild's enumeration mirror plus lib_byteid's completeness scan
still skipped the retired artifact form (the same silent
accommodation just removed from both drivers — dropping it here
surfaced and flushed 39 stale untracked amalgamator outputs across
lib/, which the gates now reject loudly). Remaining mentions are
past-tense history or quoted diagnostics.

test/wcc/993_ww_ww.c

@@ -9,7 +9,7 @@
  *     `use` resolution + the -I search path + the libwwrt.a link.
  *
  * Each build runs from a per-driver scratch directory so the
- * intermediate .combined.ww/.s/.o files don't collide.
+ * intermediate .s/.o files don't collide.
  */
 #include <stdio.h>
 #include <stdlib.h>
@@ -72,7 +72,7 @@ build_via(const char *bin, const char *driver, const char *src,
 {
 	char cmd[4096];
 	/* -o <workdir>/<out> keeps the binary where the diff expects it AND
-	 * routes the .combined.ww/.s/.o into the workdir (T3) — no longer
+	 * routes the .s/.o intermediates into the workdir (T3) — no longer
 	 * next to the source, so concurrent driver builds never collide. */
 	if (incs && incs[0]) {
 		snprintf(cmd, sizeof cmd,