fix and let bindings

Author: aspeddro

grammar.js

@@ -468,7 +468,7 @@ module.exports = grammar({
         '=',
         repeat($.decorator),
         $.expression,
-        repeat(alias($._let_binding_and, $.let_binding)),
+        optional(alias($._let_binding_and, $.let_binding)),
       )),
     ),
 

test/corpus/let_bindings.txt

@@ -257,11 +257,11 @@ and b = c
         (decorator (decorator_identifier))
         (decorator (decorator_identifier))
         (value_identifier)
-        (value_identifier))
+        (value_identifier)
       (let_binding
         (decorator (decorator_identifier))
         (value_identifier)
-        (number)))))
+        (number))))))
 
 ===========================================
 Labled function with uncurried