Remove the Travis + Bazel build. (#2071)
Remove the Travis + Bazel build. (#2071)

The Kokoro:Ubuntu build is also using Bazel, we do not need two separate
builds to check that Bazel works.

I left the TEST_BAZEL_AS_DEPENDENCY=yes build on, because this is the
only build where we check that including `google-cloud-cpp` as a Bazel
dependency works.
googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp