scip_backend: Remove use of deprecated sage.ext.memory_allocator

[mkoeppe]

📚 Description

Fixes #34941

📝 Checklist

• I have made sure that the title is self-explanatory and the description concisely explains the PR.
• I have linked an issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[github-actions]

Documentation preview for this PR is ready! 🎉
Built with commit: e736b5d

[codecov-commenter]

Codecov Report

Base: 88.58% // Head: 88.58% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (e736b5d) compared to base (293dd72).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #35101   +/-   ##
========================================
  Coverage    88.58%   88.58%           
========================================
  Files         2140     2140           
  Lines       396961   396961           
========================================
+ Hits        351655   351666   +11     
+ Misses       45306    45295   -11     

Impacted Files	Coverage Δ
src/sage/modular/hecke/algebra.py	94.65% <0.00%> (-1.07%)	⬇️
src/sage/modular/modform/numerical.py	94.19% <0.00%> (-0.65%)	⬇️
src/sage/rings/polynomial/ore_polynomial_ring.py	89.40% <0.00%> (-0.43%)	⬇️
src/sage/schemes/elliptic_curves/cardinality.py	87.00% <0.00%> (-0.40%)	⬇️
src/sage/modular/arithgroup/arithgroup_perm.py	92.57% <0.00%> (-0.38%)	⬇️
src/sage/graphs/graph_plot.py	84.33% <0.00%> (-0.29%)	⬇️
src/sage/quadratic_forms/ternary_qf.py	67.12% <0.00%> (-0.20%)	⬇️
src/sage/rings/function_field/ideal.py	89.47% <0.00%> (-0.17%)	⬇️
src/sage/combinat/posets/poset_examples.py	88.53% <0.00%> (-0.15%)	⬇️
src/sage/graphs/digraph.py	92.58% <0.00%> (-0.13%)	⬇️
... and 11 more

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[kliem]

Do you know of plans to remove unused imports with a linter?

[mkoeppe]

Thanks for the review!

I think pycodestyle can catch unused imports, but probably not for Cython modules, and also it's not part of our minimal configuration of pycodestyle, I think.

Also pyright probably includes warnings about that within its huge output