Pin Bazel version to 8.5.0.

This is the suggested workaround for https://github.com/actions/runner-images/issues/13564

PiperOrigin-RevId: 859156610

.bazelversion

diff --git a/.bazelversion b/.bazelversion
new file mode 100644
index 0000000..6d28907
--- /dev/null
+++ b/.bazelversion
@@ -0,0 +1 @@
+8.5.0