Stop testing docs in Travis
Let's rely on the ReadTheDocs pull request check instead. This does mean
that `nox -rs docs` won't get exercised by continuous integration, which
is an acceptable compromise.
@@ -32,10 +32,6 @@ jobs:
allow_failures:
- python: nightly
include:
- # Lint & documentation.
- - python: 3.8
- env: NOX_SESSION=docs
-
# Unit tests
- python: 2.7
env: NOX_SESSION=test-2.7
