mjit.c: remove wrongly-committed debug code

mistake in r65279.

=== Optcarrot Benchmark ===
$ benchmark-driver benchmark.yml --rbenv 'before::before --disable-gems --jit;after::after --disable-gems --jit' -v --repeat-count 24
before: ruby 2.6.0dev (2018-10-21 trunk 65277) +JIT [x86_64-linux]
after: ruby 2.6.0dev (2018-10-21 trunk 65279) +JIT [x86_64-linux]
last_commit=mjit.c: remove wrongly-committed debug code
Calculating -------------------------------------
                             before       after
Optcarrot Lan_Master.nes     85.008      86.078 fps

Comparison:
             Optcarrot Lan_Master.nes
                   after:        86.1 fps
                  before:        85.0 fps - 1.01x  slower

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65280 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/ruby_vm/views/_mjit_compile_send.erb

@@ -15,7 +15,6 @@
 % end
 % # compiler: Use copied cc to avoid race condition
     CALL_CACHE cc_copy = status->cc_entries + (cc - body->cc_entries);
-    cc_copy = cc;
 %
     if (has_valid_method_type(cc)) {
         const rb_iseq_t *iseq;