Fix a warning in activation hack snippet

In particular,

```
/path/to/bundler/tmp/1/bundled_app/activation_warning_hack.rb:9: warning: `*' interpreted as argument prefix
```

1 files changed, 1 insertions, 1 deletions

diff --git a/spec/runtime/setup_spec.rb b/spec/runtime/setup_spec.rb
index 24f3803f3c..e4a9dc95cd 100644
--- a/spec/runtime/setup_spec.rb
+++ b/spec/runtime/setup_spec.rb
@@ -1218,7 +1218,7 @@ end
             unless #{exemptions.inspect}.include?(name)
               warn '-' * 80
               warn "activating \#{full_name}"
-              warn *caller
+              warn(*caller)
               warn '*' * 80
             end
             bundler_spec_activate