Apply go fix modernizations

cmd/qrunproxy/show.go

@@ -1,5 +1,7 @@
 package main
 
+import "strings"
+
 import "fmt"
 
 type Show struct {
@@ -30,11 +32,12 @@ type Trigger struct {
 }
 
 func (t *Trigger) String() string {
-	s := fmt.Sprintf("%s/%s ->", t.Source.Block, t.Source.Signal)
+	var s strings.Builder
+	s.WriteString(fmt.Sprintf("%s/%s ->", t.Source.Block, t.Source.Signal))
 	for _, target := range t.Targets {
-		s += fmt.Sprintf(" %s/%s", target.Block, target.Hook)
+		s.WriteString(fmt.Sprintf(" %s/%s", target.Block, target.Hook))
 	}
-	return s
+	return s.String()
 }
 
 type TriggerSource struct {