Add deprecation notice to schema builder README

[t92549]

Related Issue

• Resolve Deprecate the schema builder tool #947

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (develop@7fadafb). Click here to learn what that means.
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@@            Coverage Diff             @@
##             develop     #950   +/-   ##
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  Coverage           ?   50.34%           
  Complexity         ?      125           
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  Files              ?       42           
  Lines              ?     1601           
  Branches           ?      130           
==========================================
  Hits               ?      806           
  Misses             ?      741           
  Partials           ?       54           

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