Resolve cmake mis-matching arguments warning

[vil02]

When configuring CMake, the output contains warning like:

  A logical block opening on the line

    /home/runner/work/CXXGraph/CXXGraph/CMakeLists.txt:22 (if)

  closes on the line

    /home/runner/work/CXXGraph/CXXGraph/CMakeLists.txt:36 (endif)

  with mis-matching arguments.
This warning is for project developers.  Use -Wno-dev to suppress it.

This PR removes it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.05%. Comparing base (b897564) to head (68a5bdb).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #548      +/-   ##
==========================================
- Coverage   97.06%   97.05%   -0.01%     
==========================================
  Files          97       97              
  Lines       11585    11585              
  Branches      768      768              
==========================================
- Hits        11245    11244       -1     
- Misses        340      341       +1     

Flag	Coverage Δ
unittests	97.05% <ø> (-0.01%)	⬇️

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