fix: increase keen's write key size constraint to 250

[yashasvibajpai]

Description of the change

Keen's write key is more than the current set size constraint of 100 characters. We are fixing it here

Checklists

Development

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

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• Changes have been reviewed by at least one other engineer
• Issue from task tracker has a link to this pull request

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (51b77b7) 100.00% compared to head (a1ba8e1) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop      #814   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines           78        78           
  Branches        13        13           
=========================================
  Hits            78        78           

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