cloud/bmaas/server/api: fix placeholder content

This just removes a small annoying error message from gazelle output.

Change-Id: I7678013aa0dc324423a0c5607dfd559a45756b83
Reviewed-on: https://review.monogon.dev/c/monogon/+/3229
Reviewed-by: Leopold Schabel <leo@monogon.tech>
Tested-by: Jenkins CI
diff --git a/cloud/bmaas/server/api/gomod-generated-placeholder.go b/cloud/bmaas/server/api/gomod-generated-placeholder.go
index e69de29..778f64e 100644
--- a/cloud/bmaas/server/api/gomod-generated-placeholder.go
+++ b/cloud/bmaas/server/api/gomod-generated-placeholder.go
@@ -0,0 +1 @@
+package api