Refactor odd memoization.
Refactor odd memoization.

It is odd here because within the matcher, we call
`@expectation = expect`, and within `expect` it was
internally memoizing, which means `@expectation`
was being assigned twice. It’s also dubious to
do so because we want to minimize internal memoization
since a matcher can be re-used against a different
target.

maclover7/rspec-mocks,edwardpark/rspec-mocks,rwz/rspec-mocks,zephyr-dev/rspec-mocks,ducthanh/rspec-mocks,edwardpark/rspec-mocks,maclover7/rspec-mocks,rspec/rspec-mocks,AEgan/rspec-mocks,zephyr-dev/rspec-mocks,rspec/rspec-mocks,rwz/rspec-mocks,telekomatrix/rspec-mocks,ducthanh/rspec-mocks,h4ck3rm1k3/rspec-mocks,telekomatrix/rspec-mocks,AEgan/rspec-mocks,h4ck3rm1k3/rspec-mocks