Add tracking branch for coreJSON

[aggarw13]

Description of changes:
git submodule update --remote -f fails for coreJSON submodule as the submodule pointer update is attempted on origin/master instead of origin/main

╰─➤  git submodule update --init -f --remote
Submodule path 'libraries/3rdparty/CMock': checked out '9c1c6a05dc7aa41d6a2da39b9f916be373ef050e'
Submodule path 'libraries/aws/device-defender-for-aws-iot-embedded-sdk': checked out '9ba281dafdf7f48941fc7f20740716883019fcfc'
Submodule path 'libraries/aws/device-shadow-for-aws-iot-embedded-sdk': checked out 'fabbece424c03f2f90a2c5b1117bcb44cbe9257b'
Submodule path 'libraries/aws/jobs-for-aws-iot-embedded-sdk': checked out '2c6628c36cb905763037265776d0d811ec7f863d'
Submodule path 'libraries/standard/coreHTTP': checked out '0882657628eb7df12dc957f9b122601fd3054a68'
fatal: Needed a single revision
Unable to find current origin/master revision in submodule path 'libraries/standard/coreJSON'

This PR fixes the issue by adding a tracking branch configuration for the coreJSON submodule.

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

[nateglims]

Other repos are converted but haven't deleted their master branch yet. Should we update them all at once?

[sarenameas]

I feel like it's lame we have to do this