Stop assuming Array#each is written in C

Same as #1015, but for Array#each.
We're thinking of rewriting it in Ruby, and I'd like to avoid failing on
test-bundled-gems in the PR.

Author: k0kubun

test/console/backtrace_test.rb

@@ -22,7 +22,7 @@ def program
     14|   end
     15| end
     16|
-    17| [1, 2, 3].each do
+    17| [1, 2, 3].reverse_each do
     18|   Foo.new.first_call
     19| end
       RUBY
@@ -33,7 +33,7 @@ def test_backtrace_prints_c_method_frame
         type 'b 18'
         type 'c'
         type 'bt'
-        assert_line_text(/\[C\] Array#each/)
+        assert_line_text(/\[C\] Array#reverse_each/)
         type 'kill!'
       end
     end

test/console/break_test.rb

@@ -388,7 +388,7 @@ def program
         2|
         3| result = ""
         4|
-        5| [1, 2, 3].each do |i|
+        5| [1, 2, 3].reverse_each do |i|
         6|   result += i.to_s
         7| end
         8|