Editorial: separate let [ into two tokens

As all the other consecutive tokens are explicitly separated into own literals, it seems beneficial to separate `let [` as well for clarity.

spec.html

@@ -16289,7 +16289,7 @@ <h1>Expression Statement</h1>
     <h2>Syntax</h2>
     <emu-grammar type="definition">
       ExpressionStatement[Yield, Await] :
-        [lookahead &lt;! {`{`, `function`, `async` [no |LineTerminator| here] `function`, `class`, `let [`}] Expression[+In, ?Yield, ?Await] `;`
+        [lookahead &lt;! {`{`, `function`, `async` [no |LineTerminator| here] `function`, `class`, `let` `[`}] Expression[+In, ?Yield, ?Await] `;`
     </emu-grammar>
     <emu-note>
       <p>An |ExpressionStatement| cannot start with a U+007B (LEFT CURLY BRACKET) because that might make it ambiguous with a |Block|. An |ExpressionStatement| cannot start with the `function` or `class` keywords because that would make it ambiguous with a |FunctionDeclaration|, a |GeneratorDeclaration|, or a |ClassDeclaration|. An |ExpressionStatement| cannot start with `async function` because that would make it ambiguous with an |AsyncFunctionDeclaration| or a |AsyncGeneratorDeclaration|.  An |ExpressionStatement| cannot start with the two token sequence `let [` because that would make it ambiguous with a `let` |LexicalDeclaration| whose first |LexicalBinding| was an |ArrayBindingPattern|.</p>
@@ -16452,10 +16452,10 @@ <h2>Syntax</h2>
       IterationStatement[Yield, Await, Return] :
         `do` Statement[?Yield, ?Await, ?Return] `while` `(` Expression[+In, ?Yield, ?Await] `)` `;`
         `while` `(` Expression[+In, ?Yield, ?Await] `)` Statement[?Yield, ?Await, ?Return]
-        `for` `(` [lookahead &lt;! {`let [`}] Expression[~In, ?Yield, ?Await]? `;` Expression[+In, ?Yield, ?Await]? `;` Expression[+In, ?Yield, ?Await]? `)` Statement[?Yield, ?Await, ?Return]
+        `for` `(` [lookahead &lt;! {`let` `[`}] Expression[~In, ?Yield, ?Await]? `;` Expression[+In, ?Yield, ?Await]? `;` Expression[+In, ?Yield, ?Await]? `)` Statement[?Yield, ?Await, ?Return]
         `for` `(` `var` VariableDeclarationList[~In, ?Yield, ?Await] `;` Expression[+In, ?Yield, ?Await]? `;` Expression[+In, ?Yield, ?Await]? `)` Statement[?Yield, ?Await, ?Return]
         `for` `(` LexicalDeclaration[~In, ?Yield, ?Await] Expression[+In, ?Yield, ?Await]? `;` Expression[+In, ?Yield, ?Await]? `)` Statement[?Yield, ?Await, ?Return]
-        `for` `(` [lookahead &lt;! {`let [`}] LeftHandSideExpression[?Yield, ?Await] `in` Expression[+In, ?Yield, ?Await] `)` Statement[?Yield, ?Await, ?Return]
+        `for` `(` [lookahead &lt;! {`let` `[`}] LeftHandSideExpression[?Yield, ?Await] `in` Expression[+In, ?Yield, ?Await] `)` Statement[?Yield, ?Await, ?Return]
         `for` `(` `var` ForBinding[?Yield, ?Await] `in` Expression[+In, ?Yield, ?Await] `)` Statement[?Yield, ?Await, ?Return]
         `for` `(` ForDeclaration[?Yield, ?Await] `in` Expression[+In, ?Yield, ?Await] `)` Statement[?Yield, ?Await, ?Return]
         `for` `(` [lookahead != `let` ] LeftHandSideExpression[?Yield, ?Await] `of` AssignmentExpression[+In, ?Yield, ?Await] `)` Statement[?Yield, ?Await, ?Return]