Bump Bazel version to 3.0.0

Change-Id: I8f941bb9b1002c558be15f73e88e250afc4e4ac0
diff --git a/.bazelversion b/.bazelversion
index ccbccc3..4a36342 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-2.2.0
+3.0.0