Update version to v1.18.7

[willhickey]

Nothing in this changeset except the version update

$ glol -1
641f9df975 2024-03-15 21:01:30 -0500  (HEAD -> version_bump_v1.18.7, origin/version_bump_v1.18.7)  [email protected] Update version to v1.18.7
$ git diff v1.18..HEAD | grep -vE "^ |^@@ |^--- |^\+\+\+ |^index |^diff |^-( \")?solana.*1.18.6|^\+( \")?solana.*1.18.7|^-version|^\+version"
$

[anza-team]

Thank you for the contribution! This repository is no longer in use. Please re-open this pull request in the agave repo: https://github.com/anza-xyz/agave