Fix comment (#34168)

The code clears the O_NONBLOCK flag (that is, makes IO blocking), so make the comment match.

Author: CitizenB

.travis.yml

@@ -75,8 +75,7 @@ matrix:
 
 before_install:
   - echo "before_install"
-  # set non-blocking IO on travis
-  # https://github.com/travis-ci/travis-ci/issues/8920#issuecomment-352661024
+  # Use blocking IO on travis.  Ref:  https://github.com/travis-ci/travis-ci/issues/8920#issuecomment-352661024
   - python -c 'import os,sys,fcntl; flags = fcntl.fcntl(sys.stdout, fcntl.F_GETFL); fcntl.fcntl(sys.stdout, fcntl.F_SETFL, flags&~os.O_NONBLOCK);'
   - source ci/travis_process_gbq_encryption.sh
   - export PATH="$HOME/miniconda3/bin:$PATH"