workspace: bump bazel to 7.2.1

Change-Id: I6cde34a1f35f77a7688089de24f7963100ede058
Reviewed-on: https://review.monogon.dev/c/monogon/+/3216
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/.bazelversion b/.bazelversion
index 66ce77b..b26a34e 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-7.0.0
+7.2.1