Remove leftover mentions of `lambdaworks-felt` feature

[fmoletta]

The feature is gone but the docs still live 🔪

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (39e8b08) 97.16% compared to head (6f94a37) 97.16%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1610 +/- ## ======================================= Coverage 97.16% 97.16% ======================================= Files 92 92 Lines 37369 37369 ======================================= Hits 36309 36309 Misses 1060 1060 ```

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[github-actions[bot]]

Benchmark Results for unmodified programs :rocket:

Command	Mean [s]	Min [s]	Max [s]	Relative
base big_factorial	2.253 ± 0.011	2.244	2.280	1.01 ± 0.01
head big_factorial	2.227 ± 0.011	2.218	2.254	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base big_fibonacci	2.242 ± 0.046	2.207	2.362	1.00 ± 0.03
head big_fibonacci	2.235 ± 0.044	2.197	2.348	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base blake2s_integration_benchmark	8.251 ± 0.088	8.150	8.377	1.01 ± 0.01
head blake2s_integration_benchmark	8.179 ± 0.067	8.112	8.298	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base compare_arrays_200000	2.292 ± 0.018	2.276	2.334	1.02 ± 0.01
head compare_arrays_200000	2.255 ± 0.013	2.236	2.285	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base dict_integration_benchmark	1.440 ± 0.007	1.434	1.457	1.00
head dict_integration_benchmark	1.440 ± 0.009	1.432	1.458	1.00 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base field_arithmetic_get_square_benchmark	1.281 ± 0.006	1.272	1.291	1.00 ± 0.01
head field_arithmetic_get_square_benchmark	1.281 ± 0.010	1.270	1.293	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base integration_builtins	8.256 ± 0.091	8.159	8.379	1.00 ± 0.01
head integration_builtins	8.240 ± 0.056	8.194	8.380	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base keccak_integration_benchmark	8.543 ± 0.189	8.385	9.017	1.01 ± 0.02
head keccak_integration_benchmark	8.485 ± 0.086	8.406	8.610	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base linear_search	2.343 ± 0.027	2.321	2.412	1.01 ± 0.01
head linear_search	2.314 ± 0.017	2.295	2.337	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base math_cmp_and_pow_integration_benchmark	1.567 ± 0.007	1.557	1.575	1.01 ± 0.01
head math_cmp_and_pow_integration_benchmark	1.548 ± 0.007	1.542	1.564	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base math_integration_benchmark	1.447 ± 0.017	1.430	1.490	1.01 ± 0.02
head math_integration_benchmark	1.434 ± 0.018	1.418	1.472	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base memory_integration_benchmark	1.279 ± 0.008	1.269	1.292	1.03 ± 0.01
head memory_integration_benchmark	1.245 ± 0.007	1.235	1.254	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base operations_with_data_structures_benchmarks	1.598 ± 0.021	1.582	1.650	1.00
head operations_with_data_structures_benchmarks	1.601 ± 0.008	1.594	1.620	1.00 ± 0.01

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
base pedersen	603.7 ± 1.5	601.7	606.4	1.00 ± 0.00
head pedersen	601.7 ± 2.1	599.0	604.9	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base poseidon_integration_benchmark	1.049 ± 0.003	1.046	1.054	1.00
head poseidon_integration_benchmark	1.051 ± 0.012	1.045	1.084	1.00 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base secp_integration_benchmark	1.925 ± 0.009	1.912	1.940	1.00 ± 0.01
head secp_integration_benchmark	1.919 ± 0.007	1.911	1.931	1.00

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
base set_integration_benchmark	768.3 ± 2.1	765.9	773.0	1.00 ± 0.01
head set_integration_benchmark	766.3 ± 6.2	762.2	783.0	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base uint256_integration_benchmark	4.575 ± 0.077	4.523	4.772	1.01 ± 0.02
head uint256_integration_benchmark	4.543 ± 0.039	4.507	4.620	1.00