WORKSPACE: bump bazel to 7.0.0

Change-Id: Ic074b7b83f229e3c7f6ace7fdb46d33e5bd7c37b
Reviewed-on: https://review.monogon.dev/c/monogon/+/2708
Reviewed-by: Serge Bazanski <serge@monogon.tech>
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/.bazelversion b/.bazelversion
index 19b860c..66ce77b 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-6.4.0
+7.0.0