Ruby: Fix regex parsing of /[|]/

ruby/ql/lib/codeql/ruby/security/performance/ParseRegExp.qll

@@ -861,6 +861,7 @@ abstract class RegExp extends AST::StringlikeLiteral {
    * Whether the text in the range start,end is an alternation
    */
   predicate alternation(int start, int end) {
+    not this.inCharSet(start) and
     this.topLevel(start, end) and
     exists(int less | this.subalternation(start, less, _) and less < end)
   }

ruby/ql/test/library-tests/regexp/parse.expected

@@ -181,11 +181,8 @@ regexp.rb:
 #   26| [RegExpConstant, RegExpNormalChar] -
 
 #   27| [RegExpCharacterClass] [|]
-#-----| 0 -> [RegExpAlt] |
 #-----| 0 -> [RegExpConstant, RegExpNormalChar] |
 
-#   27| [RegExpAlt] |
-
 #   27| [RegExpConstant, RegExpNormalChar] |
 
 #   30| [RegExpCharacterClass] [[a-f]