Set DART_ENABLE_SIMD=OFF by default

[jslee02]

gazebosim/gz-physics#662

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Before creating a pull request

• Document new methods and classes
• Format new code files using ClangFormat by running make format
• Build with -DDART_TREAT_WARNINGS_AS_ERRORS=ON and resolve all the compile warnings

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• Add unit test(s) for this change
• Add Python bindings for new methods and classes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.57%. Comparing base (4138ff2) to head (2d21c25).
Report is 12 commits behind head on release-6.14.

Additional details and impacted files

@@              Coverage Diff              @@
##           release-6.14    #1825   +/-   ##
=============================================
  Coverage         61.56%   61.57%           
=============================================
  Files               490      490           
  Lines             46021    46021           
=============================================
+ Hits              28334    28337    +3     
+ Misses            17687    17684    -3     

see 1 file with indirect coverage changes

[mderbaso-deepx]

Just curious, any performance measurements for this change were made?