typo in 2016-10-31.md

[oltruong]

Issue #, if available:

Description of changes:
just a small typo
Description of how you validated changes:

Checklist:

• Write/update tests
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected
• Add/update example to examples/2016-10-31

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #979 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #979   +/-   ##
=======================================
  Coverage   94.62%   94.62%           
=======================================
  Files          69       69           
  Lines        2997     2997           
  Branches      554      554           
=======================================
  Hits         2836     2836           
  Misses         85       85           
  Partials       76       76

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