docs: update release note for 1.4.0 release

[chr1shung]

Signed-off-by: Chris Hung [email protected]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

If your build fails due to your commit message not passing the build checks, please review the guidelines here: https://github.com/edgexfoundry/device-sdk-c/blob/master/.github/CONTRIBUTING.md

What is the current behavior?

Issue Number:

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

New Imports

• Yes
• No

Specific Instructions

Other information

[codecov-io]

Codecov Report

Merging #703 (00c0363) into master (bb51c8d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #703   +/-   ##
=======================================
  Coverage   45.35%   45.35%           
=======================================
  Files          32       32           
  Lines        3122     3122           
=======================================
  Hits         1416     1416           
  Misses       1593     1593           
  Partials      113      113           

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[cloudxxx8]

LGTM