delete GPU implementation

[j-i-k-o]

Changes

• delete the USE_CUDA section as the GPU algorithm is no longer supported.
• delete GPU code from python

Destructive changes

• This PR affects the existing codes using GPU algorithms. Note that these changes do not affect the practical use of OpenJij since the GPU algorithm is no longer supported (current GPU implementation is only for specific graph topology and cannot overperform CPU implementation).

[codecov]

Codecov Report

Merging #387 (abffd2a) into main (7fefc56) will increase coverage by 1.84%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #387      +/-   ##
==========================================
+ Coverage   70.53%   72.38%   +1.84%     
==========================================
  Files          46       42       -4     
  Lines        2671     2567     -104     
  Branches      977      925      -52     
==========================================
- Hits         1884     1858      -26     
+ Misses        501      423      -78     
  Partials      286      286              

Flag	Coverage Δ
cxxopenjij	68.24% <ø> (ø)
openjij	67.30% <0.00%> (+3.82%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
openjij/model/chimera_model.py	28.34% <0.00%> (+0.65%)	⬆️
openjij/model/model.py	92.28% <ø> (-0.05%)	⬇️

... and 1 file with indirect coverage changes

[codeclimate]

Code Climate has analyzed commit abffd2a and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 0.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 60.7% (4.6% change).

View more on Code Climate.