chore: some cosmetic changes

grammar.js

@@ -132,7 +132,7 @@ module.exports = grammar({
     insert_items: ($) =>
       choice(
         seq(kw("default"), kw("values")),
-        seq(kw("values"), $.insert_values, repeat(seq(",", $.insert_values))),
+        seq(kw("values"), commaSep1($.insert_values)),
         $.select_statement,
         seq("(", $.select_statement, ")")
       ),

src/grammar.json

@@ -841,6 +841,9 @@
               "named": false,
               "value": "values"
             },
+            {
+              "type": "SEQ",
+              "members": [
                 {
                   "type": "SYMBOL",
                   "name": "insert_values"
@@ -862,6 +865,8 @@
                   }
                 }
               ]
+            }
+          ]
         },
         {
           "type": "SYMBOL",