Update Findfcl.cmake to support FCL 0.6

[jslee02]

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Before creating a pull request

• [N/A] Document new methods and classes
• [N/A] Format new code files using clang-format

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• [N/A] Add unit test(s) for this change

[codecov]

Codecov Report

Merging #1441 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1441      +/-   ##
==========================================
- Coverage   58.00%   57.99%   -0.02%     
==========================================
  Files         412      412              
  Lines       29861    29861              
==========================================
- Hits        17322    17319       -3     
- Misses      12539    12542       +3     

Impacted Files	Coverage Δ
dart/dynamics/Skeleton.cpp	66.16% <0.00%> (-0.17%)	⬇️