ci: make iai-callgrind PR comments non-blocking

[samueltardieu]

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[github-actions]

📊 iai-callgrind Benchmark Results

➡️ 20 Unchanged (within ±0.1%)

Click to expand

Benchmark	Instructions
iai_algos::corner_to_corner_astar	103
iai_algos::corner_to_corner_bfs	103
iai_algos::corner_to_corner_bfs_bidirectional	2,797,734
iai_algos::corner_to_corner_dfs	2,854,816
iai_algos::corner_to_corner_dijkstra	103
iai_algos::corner_to_corner_fringe	103
iai_algos::corner_to_corner_idastar	71,150
iai_algos::corner_to_corner_iddfs	251
iai_algos::no_path_astar	14
iai_algos::no_path_bfs	14
iai_algos::no_path_bfs_bidirectional	16
iai_algos::no_path_dfs	2,734,235
iai_algos::no_path_dijkstra	14
iai_algos::no_path_fringe	3,865,136
iai_edmondskarp::wikipedia_example_dense	38,293
iai_edmondskarp::wikipedia_example_sparse	65,834
iai_kuhn_munkres::kuhn_munkres_size_128	4,179,468
iai_kuhn_munkres::kuhn_munkres_size_32	258,587
iai_kuhn_munkres::kuhn_munkres_size_64	1,228,805
iai_separate_components::bench_separate_components	16,468,160

✅ All benchmarks unchanged

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iai-callgrind measures instructions executed, which is deterministic and not affected by system load.