Add a comment and `TODO` about the action key determinism test.

PiperOrigin-RevId: 409167032
diff --git a/src/test/shell/integration/aquery_test.sh b/src/test/shell/integration/aquery_test.sh
index 72512e0..44c328b 100755
--- a/src/test/shell/integration/aquery_test.sh
+++ b/src/test/shell/integration/aquery_test.sh
@@ -1490,6 +1490,9 @@
 }
 
 # Regression test for b/205753626.
+# This test case isn't testing aquery for correctness, just using aquery as a
+# vehicle for testing lower-level logic.
+# TODO(b/205978333): Find a better home for this test case.
 function test_starlark_action_with_reqs_has_deterministic_action_key() {
   local -r pkg="${FUNCNAME[0]}"
   mkdir -p "$pkg" || fail "mkdir -p $pkg"