doc: Update FAQ

[dweindl]

Remove outdated BLAS issue, add C++20 issue.

Closes #3162.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.50%. Comparing base (be3ed58) to head (cc5b931).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3173      +/-   ##
==========================================
- Coverage   78.14%   77.50%   -0.64%     
==========================================
  Files         317      317              
  Lines       20772    20772              
  Branches     1484     1483       -1     
==========================================
- Hits        16232    16100     -132     
- Misses       4532     4664     +132     
  Partials        8        8              

Flag	Coverage Δ
cpp	70.09% <ø> (ø)
cpp_python	36.92% <ø> (ø)
petab	46.91% <ø> (ø)
petab_sciml	15.01% <ø> (ø)
python	68.58% <ø> (ø)
sbmlsuite-jax	?

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see 4 files with indirect coverage changes

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