[collectors]: fix typo in test assertion

Signed-off-by: Max Coplan <mchcopl@gmail.com>>

prometheus/collectors/go_collector_latest_test.go

@@ -50,7 +50,7 @@ func TestGoCollectorMarshalling(t *testing.T) {
 	}
 
 	if _, err := json.Marshal(result); err != nil {
-		t.Errorf("json marshalling shoud not fail, %v", err)
+		t.Errorf("json marshalling should not fail, %v", err)
 	}
 }