fix(agent): restore the !linux build constraint on collect_other.go

Unrelated to the shared module work; pre-existing on main.

"_other" is not a GOOS suffix, so without the constraint this file compiled
on Linux alongside collect_linux.go and redeclared collect. Linux agent
builds failed, which agent-release.yml depends on.

agent/internal/inventory/collect_other.go

@@ -1,5 +1,9 @@
+//go:build !linux
 
-
+// Inventory collection is Linux-only. This no-op stands in everywhere else.
+//
+// The build constraint above is load-bearing: "_other" is not a GOOS suffix, so
+// without it this file compiles on Linux too and collides with collect_linux.go.
 package inventory
 
 import "github.com/mrhid6/vantage/agent/internal/grpc/pb"