[ruby/erb] Escape the second *

The original code just seems unintentional

https://github.com/ruby/erb/commit/75a0749cb7

lib/erb.rb

@@ -724,7 +724,7 @@ class ERB
       frozen = nil
       s.scan(re) do
         comment = $+
-        comment = $1 if comment[/-\*-\s*([^\s].*?)\s*-*-$/]
+        comment = $1 if comment[/-\*-\s*([^\s].*?)\s*-\*-$/]
         case comment
         when %r"coding\s*[=:]\s*([[:alnum:]\-_]+)"
           enc = Encoding.find($1.sub(/-(?:mac|dos|unix)/i, ''))