Evergreen link updates

- remove link from public README
- in release procedure documentation note that auth is required

Author: rcsanchez97

README.md

@@ -1,6 +1,5 @@
 # MongoDB C++ Driver 
 [![Travis Build Status](https://travis-ci.org/mongodb/mongo-cxx-driver.svg?branch=master)](https://travis-ci.org/mongodb/mongo-cxx-driver)
-[![Evergreen Build Status](https://img.shields.io/badge/build-evergreen-brightgreen)](https://evergreen.mongodb.com/waterfall/cxx-driver)
 [![codecov](https://codecov.io/gh/mongodb/mongo-cxx-driver/branch/master/graph/badge.svg)](https://codecov.io/gh/mongodb/mongo-cxx-driver)
 [![Documentation](https://img.shields.io/badge/docs-doxygen-blue.svg)](https://mongocxx.org/api/mongocxx-v3/)
 [![Documentation](https://img.shields.io/badge/docs-mongocxx-green.svg)](https://mongocxx.org/)

etc/releasing.md

@@ -6,9 +6,9 @@ If doing a release on a version prior to 3.5.0, follow the old instructions from
 Ensure the latest commit has run tests on the Evergreen waterfall.
 
 For a minor release this should be the waterfall tracking the master branch:
-https://evergreen.mongodb.com/waterfall/cxx-driver
+https://evergreen.mongodb.com/waterfall/cxx-driver (requires auth)
 For a patch release this is the waterfall tracking that branch. E.g. if you are releasing 3.7.1, then the waterfall tracking releases/v3.7:
-https://spruce.mongodb.com/commits/cxx-driver-v3.7
+https://spruce.mongodb.com/commits/cxx-driver-v3.7 (requires auth)
 
 If there are test failures, ensure they are at least expected or not introduced by changes in the new release.