chore: update checkout in next run workflows

[alexghr]

Bump actions/checkout to v6 to resolve Nodejs 20 warnings

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 2 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/02df0dd3089d899c�02df0dd3089d899c8;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_p2p/broadcasted_invalid_block_proposal_slash.test.ts (218s) (code: 0) group:e2e-p2p-epoch-flakes
\033FLAKED\033 (8;;http://ci.aztec-labs.com/63ad97466be1d836�63ad97466be1d8368;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_p2p/multiple_validators_sentinel.parallel.test.ts "collects attestations for all validators on a node" (345s) (code: 0) group:e2e-p2p-epoch-flakes