.bazelversion: use 5.2.0, as that's what we use in nix

Change-Id: Ia64cb4d86f590992116c26b027860a554cc74ec6
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1531
Reviewed-by: q3k <q3k@hackerspace.pl>
diff --git a/.bazelversion b/.bazelversion
index ade6522..91ff572 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-5.4.1
+5.2.0