Allow OP_RETURN_BLK to cross C boundaries

The restriction was introduced in commit b563bcb7ff to resolve https://github.com/mruby/mruby/issues/3462.
Subsequently, the `RBreak` object, introduced by mruby 1.3.0, allowed crossing the C boundary.

```ruby
def cross; Class.new { proc { return }.call }; end; cross
# => unexpected return (LocalJumpError) # without this patch
# => nothing raised                     # with this patch
```

src/vm.c

@@ -2319,10 +2319,6 @@ RETRY_TRY_BLOCK:
       }
       /* check jump destination */
       while (cibase <= ci && ci->proc != dst) {
-        if (ci->cci > CINFO_NONE) { /* jump cross C boundary */
-          localjump_error(mrb, LOCALJUMP_ERROR_RETURN);
-          goto L_RAISE;
-        }
         ci--;
       }
       if (ci <= cibase) { /* no jump destination */