Use a new config instance for these specs.
Use a new config instance for these specs.

- Makes the `it "is false by default"` spec more accurate (as a new
  instance demonstrates the default more accurately then manually
  setting it to `nil`).
- Prevents the changes here from "leaking" into other specs;
  previously, the mutation to the global config could affect
  other specs.

bjpcjp/rspec-expectations,AEgan/rspec-expectations,unmanbearpig/rspec-expectations,zsyed91/rspec-expectations,alexaltair/rspec-expectations,emilyforst/rspec-expectations,edwardpark/rspec-expectations,rspec/rspec-expectations,yaoshipu/rspec-expectations,bjpcjp/rspec-expectations,jamelablack/rspec-expectations,jdax/rspec-expectations,jasonkarns/rspec-expectations,maclover7/rspec-expectations,rspec/rspec-expectations,maclover7/rspec-expectations,AEgan/rspec-expectations,alexaltair/rspec-expectations,chrisarcand/rspec-expectations,jdax/rspec-expectations,zsyed91/rspec-expectations,emilyforst/rspec-expectations,jasonkarns/rspec-expectations,chrisarcand/rspec-expectations,yaoshipu/rspec-expectations,h4ck3rm1k3/rspec-expectations,dg-ratiodata/rspec-expectations,dg-ratiodata/rspec-expectations,unmanbearpig/rspec-expectations,edwardpark/rspec-expectations,h4ck3rm1k3/rspec-expectations,jamelablack/rspec-expectations