Fix buffer overflow for Julia >=1.11 in mpfr_strtofr

[Zentrik]

Closes #189. If a new release could be cut once this is merged that would be useful.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.97%. Comparing base (6e12d5f) to head (d4f3df9).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/floats.jl	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #193      +/-   ##
==========================================
- Coverage   88.41%   86.97%   -1.44%     
==========================================
  Files          10        9       -1     
  Lines        1891     1874      -17     
==========================================
- Hits         1672     1630      -42     
- Misses        219      244      +25     

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