travis: Update CI to not use log feature

Author: josephlr

.travis.yml

@@ -91,14 +91,13 @@ matrix:
         - cargo test --benches
         # Check that setting various features does not break the build
         - cargo build --features=std
-        - cargo build --features=log
         # remove cached documentation, otherwise files from previous PRs can get included
         - rm -rf target/doc
         - cargo doc --no-deps --features=std
         - cargo deadlinks --dir target/doc
         # also test minimum dependency versions are usable
         - cargo generate-lockfile -Z minimal-versions
-        - cargo test --features=std,log
+        - cargo test --features=std
 
     - <<: *nightly_and_docs
       name: "OSX, nightly, docs"