Updates version number to 0.4.374474001.20210518.
Updates version number to 0.4.374474001.20210518.

PiperOrigin-RevId: 374489201
(cherry picked from commit 21cc1c85ac04b1e126b40726ed9fb371e2fea1bc)

bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi