[bazel] update .bazelversion to 8.0.0

Fixes:

    ERROR: The project you're trying to build requires Bazel 7.3.0 (specified
    in llvm-project/utils/bazel/.bazelversion), but it wasn't found in
    /usr/bin.

    You can install the required Bazel version via apt:
      sudo apt update && sudo apt install bazel-7.3.0

    If this doesn't work, check Bazel's installation instructions for help:
      https://bazel.build/install/ubuntu

Link: https://blog.bazel.build/2024/12/09/bazel-8-release.html

Author: nickdesaulniers

utils/bazel/.bazelversion

@@ -1 +1 @@
-7.3.0
+8.0.0