Remove unused CMake options for break tests

[andrewhop]

Description of changes:

Setting the CMake option FIPS_BREAK_TEST to something like FFC_DH would result in defining BORINGSSL_FIPS_BREAK_FFC_DH=1 which used to be how the break tests were broken. break-kat.go replaced all of that and all the code using the definitions were removed. 913af96 removed the last legacy usage of it.

The correct way to test breaking AWS-LC is outlined in FIPS.md:

1. Compile with BORINGSSL_FIPS_BREAK_TESTS defined
2. Run break-kat.go to break a certain CAST

This also removes the note about fips_break_tests.h since that file doesn't exist anymore.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.04%. Comparing base (95b1fad) to head (244a383).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2249      +/-   ##
==========================================
- Coverage   79.04%   79.04%   -0.01%     
==========================================
  Files         612      612              
  Lines      106517   106513       -4     
  Branches    15053    15053              
==========================================
- Hits        84200    84193       -7     
- Misses      21666    21667       +1     
- Partials      651      653       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.