F2.2: un-workaround 0714 — combine string == under and/or (0078 fixed)

Issue 0078 (string == as an and/or operand emitting an invalid PHI) is
resolved on this branch, so the example no longer needs the split that
worked around it. Restore the natural combined assertion
  sub.items[0].key == "k" and sub.items[0].val.str == "v"
(one nested-pair report), and the in_range containment helper to
  return x >= lo and x < hi;
Drop the now-stale issues/0078 references. Re-captured expected stdout
(nested-key/nested-val -> nested-pair). json.sx and src/ untouched.

examples/expected/0714-modules-json-reader.stdout

@@ -8,8 +8,7 @@ array-pos: ok
 array-neg: ok
 bool-value: ok
 null-value: ok
-nested-key: ok
-nested-val: ok
+nested-pair: ok
 plain-is-view: ok
 escaped-allocated: ok
 round-trip: ok