chore: remove conformance-tests (#167)

Conformance tests are no longer built via this repo, the testbench server has been split to its own repo and its build is managed there. https://github.com/googleapis/storage-testbench

Author: BenWhitehead

.github/CODEOWNERS

@@ -11,4 +11,3 @@
 /node       @googleapis/yoshi-nodejs
 /python     @googleapis/yoshi-python
 /ruby       @googleapis/yoshi-ruby
-/conformance-tests  @googleapis/cloud-storage-dpes