Adjust expected eval backtrace

Author: eregon

test/truffle/integration/backtraces/eval.backtrace

@@ -1,11 +1,8 @@
 (eval):1:in `m3': message (RuntimeError)
-	from <internal:core> core/kernel.rb:LINE:in `eval'
 	from /eval.rb:22:in `m3'
 	from a_m3_calling_source.rb:42:in `m2'
-	from <internal:core> core/kernel.rb:LINE:in `eval'
 	from /eval.rb:18:in `m2'
 	from (eval):1:in `m1'
-	from <internal:core> core/kernel.rb:LINE:in `eval'
 	from /eval.rb:14:in `m1'
 	from /eval.rb:26:in `block in <main>'
 	from /backtraces.rb:17:in `check'