Fix typo

Author: ondrejmirtes

Diff for: UPGRADING.md

@@ -118,7 +118,7 @@ Now, `throw $e;` is represented as a `Stmt\Expression` that contains an `Expr\Th
 See [UPGRADING](https://github.com/phpstan/phpdoc-parser/blob/2.0.x/UPGRADING.md) guide for phpstan/phpdoc-parser.
 
 ### Returning plain strings as errors no longer supported, use RuleErrorBuilder
-    *
+
 Identifiers are also required in custom rules.
 
 Learn more: [Using RuleErrorBuilder to enrich reported errors in custom rules](https://phpstan.org/blog/using-rule-error-builder)