[llvm] [bazel] update .bazelversion to 8.0.0 (PR #119425)

[Keith Smiley via llvm-commits]

keith wrote:

I bisected to https://github.com/bazelbuild/bazel/commit/52105e30199a791ba2a2e7249d5e8515165fbdfd, it's a known issue that we rely on this, we just need to flip it back for now: https://github.com/llvm/llvm-project/pull/119462

https://github.com/llvm/llvm-project/pull/119425