docs: remove unused SMS config from schema

[zepatrik]

This part of the schema is not used, and we already introduced the SMS config elsewhere.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.57%. Comparing base (82660f0) to head (168201a).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4212      +/-   ##
==========================================
+ Coverage   78.54%   78.57%   +0.02%     
==========================================
  Files         380      380              
  Lines       27225    27225              
==========================================
+ Hits        21384    21392       +8     
+ Misses       4218     4214       -4     
+ Partials     1623     1619       -4     

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