multi: update comment on changing Go version

Since we now have a scripted check that makes sure the Golang version is
synced throughout all files, it is important that the main version in
the Makefile is changed, then all other versions can be detected by that
script.

go.mod

@@ -207,8 +207,9 @@ replace github.com/gogo/protobuf => github.com/gogo/protobuf v1.3.2
 // allows us to specify that as an option.
 replace google.golang.org/protobuf => github.com/lightninglabs/protobuf-go-hex-display v1.30.0-hex-display
 
-// If you change this please also update .github/pull_request_template.md,
-// docs/INSTALL.md and GO_IMAGE in lnrpc/gen_protos_docker.sh.
+// If you change this please also update docs/INSTALL.md and GO_VERSION in
+// Makefile (then run `make lint` to see where else it needs to be updated as
+// well).
 go 1.22.6
 
 retract v0.0.2