PHPLIB-1710: Remove dead local .evergreen config (#1766)

* Remove `.evergreen/ocsp` directory

As it seems to be covered by the `drivers-evergreen-tools` submodule,
which is loaded in evergreen functions and GH actions (added in PR
`#1584`)

* Clean up `.evergreen/orchestration` directory

Its contents don't seem to be used

* Clean up `.evergreen/auth_aws`

It doesn't appear to be referenced locally anymore, only internally in the
drivers-evergreen-tools submodule

* Clean up`.evergreen/x509gen` directory

There's no need for it locally as it's covered by
the `drivers-everygreen-tools` submodule

Author: paulinevos