treewide: cleanup error string formatting

Change-Id: I9012ba58dded916984468219b214200144a439b9
Reviewed-on: https://review.monogon.dev/c/monogon/+/3023
Reviewed-by: Serge Bazanski <serge@monogon.tech>
Vouch-Run-CI: Tim Windelschmidt <tim@monogon.tech>
Tested-by: Jenkins CI
diff --git a/cloud/agent/install.go b/cloud/agent/install.go
index f209ce3..5b0c209 100644
--- a/cloud/agent/install.go
+++ b/cloud/agent/install.go
@@ -52,6 +52,7 @@
 
 func installMetropolis(req *bpb.MetropolisInstallationRequest, netConfig *npb.Net, l logtree.LeveledLogger, isEFIBoot bool) error {
 	if !isEFIBoot {
+		//nolint:ST1005
 		return errors.New("Monogon OS can only be installed on EFI-booted machines, this one is not")
 	}