Editorial: Simplify the 'Term' production

... by merging three pairs of RHSs.

(Preserves the order of alternatives under [~U], but not under [+U],
but that's okay, because the [+U] sides aren't order-disambiguated.)

spec.html

@@ -30304,13 +30304,10 @@ <h2>Patterns</h2>
           Alternative[?U, ?N] Term[?U, ?N]
 
         Term[U, N] ::!
-          [+U] Assertion[+U, ?N]
-          [+U] Atom[+U, ?N]
-          [+U] Atom[+U, ?N] Quantifier
           [~U] QuantifiableAssertion[~U, ?N] Quantifier
-          [~U] Assertion[~U, ?N]
-          [~U] Atom[~U, ?N] Quantifier
-          [~U] Atom[~U, ?N]
+          Assertion[?U, ?N]
+          Atom[?U, ?N] Quantifier
+          Atom[?U, ?N]
 
         Assertion[U, N] ::
           `^`