Refactored as requested in PR and updated fail test accordingly

Author: LucaCappelletti94

src/parser/mod.rs

@@ -5625,9 +5625,7 @@ impl<'a> Parser<'a> {
                 TriggerObjectKind::For(trigger_object)
             })
         } else {
-            if !dialect_of!(self is SQLiteDialect ) {
-                self.expect_keyword_is(Keyword::FOR)?;
-            }
+            let _ = self.parse_keyword(Keyword::FOR);
 
             None
         };

tests/sqlparser_postgres.rs

@@ -5869,7 +5869,7 @@ fn parse_create_trigger_invalid_cases() {
     let invalid_cases = vec![
         (
             "CREATE TRIGGER check_update BEFORE UPDATE ON accounts FUNCTION check_account_update",
-            "Expected: FOR, found: FUNCTION"
+            "Expected: an SQL statement, found: FUNCTION"
         ),
         (
             "CREATE TRIGGER check_update TOMORROW UPDATE ON accounts EXECUTE FUNCTION check_account_update",