Editorial: Simplify the 'Atom' production

... by merging the two capturing-group alternatives.

(This may be affected by the outcome of issue tc39#1673.)

spec.html

@@ -31049,8 +31049,7 @@ <h2>Patterns</h2>
           `\` AtomEscape[?U, ?N]
           [~U] `\` [lookahead == `c`]
           CharacterClass[?U]
-          [+U] `(` GroupSpecifier[?U] Disjunction[?U, ?N] `)`
-          [~U] `(` Disjunction[?U, ?N] `)`
+          `(` GroupSpecifier[?U] Disjunction[?U, ?N] `)`
           `(` `?` `:` Disjunction[?U, ?N] `)`
           [~U] InvalidBracedQuantifier
           [+U] PatternCharacter
@@ -31075,7 +31074,7 @@ <h2>Group Specifiers</h2>
       <emu-grammar type="definition">
         GroupSpecifier[U] ::
           [empty]
-          `?` GroupName[?U]
+          [+U] `?` GroupName[?U]
 
         GroupName[U] ::
           `&lt;` RegExpIdentifierName[?U] `&gt;`
@@ -31781,8 +31780,6 @@ <h1>Term</h1>
           1. Return an internal Matcher closure that takes two arguments, a State _x_ and a Continuation _c_, and performs the following steps:
             1. Call RepeatMatcher(_m_, _min_, _max_, _greedy_, _x_, _c_, _parenIndex_, _parenCount_) and return its result.
         </emu-alg>
-        <p>----</p>
-        <p>In the above algorithm, references to <emu-grammar>Atom :: `(` GroupSpecifier Disjunction `)`</emu-grammar> are to be interpreted as meaning <emu-grammar>Atom :: `(` GroupSpecifier Disjunction `)`</emu-grammar> or <emu-grammar>Atom :: `(` Disjunction `)`</emu-grammar> .</p>
         <p>The production <emu-grammar>Term :: QuantifiableAssertion Quantifier</emu-grammar> evaluates the same as the production <emu-grammar>Term :: Atom Quantifier</emu-grammar> but with |QuantifiableAssertion| substituted for |Atom|.</p>
 
         <emu-clause id="sec-runtime-semantics-repeatmatcher-abstract-operation" aoid="RepeatMatcher">