mathlib

1611b30c - refactor(combinatorics/simple_graph): simplify proofs (#6115)

refactor(combinatorics/simple_graph): simplify proofs (#6115) Co-authors: `lean-gptf`, Stanislas Polu This was found by `formal-lean-wm-to-tt-m1-m2-v4-c4` when we evaluated it on theorems added to `mathlib` after we last extracted training data.