Comment # 6 on bug 64177 from Patrick Ohly

I noticed an inconsistency: the operations should use hyphen instead of
underscore, like the other string constants. I noticed because I mistyped them
in the tests at first.

I'll make it consistent, so now the operations are:

-    [ 'is|contains|begins_with|ends_with', '<field>', '<text>',
+    [ 'is|contains|begins-with|ends-with', '<field>', '<text>',