[ruby/win32ole] Use `end_with?` and fix indent

https://github.com/ruby/win32ole/commit/7648ee7e56

ext/win32ole/sample/olegen.rb

@@ -70,7 +70,7 @@ class WIN32COMGen
     end
     if ts.empty?
       ts = 'VT_VARIANT'
-    elsif ts[-1] == ?|
+    elsif ts.end_with?(?|)
       ts += 'VT_VARIANT'
     end
     ts