chore(decoder): use unsafe.String

This raises the minimum Go version to 1.20

README.md

@@ -14,7 +14,7 @@ D-Bus message bus system.
 
 ### Installation
 
-This packages requires Go 1.12 or later. It can be installed by running the command below:
+This packages requires Go 1.20 or later. It can be installed by running the command below:
 
 ```
 go get github.com/godbus/dbus/v5

decoder.go

@@ -370,12 +370,6 @@ func (c *stringConverter) String(b []byte) string {
 }
 
 // toString converts a byte slice to a string without allocating.
-// Starting from Go 1.20 you should use unsafe.String.
 func toString(b []byte) string {
-	var s string
-	h := (*reflect.StringHeader)(unsafe.Pointer(&s))
-	h.Data = uintptr(unsafe.Pointer(&b[0]))
-	h.Len = len(b)
-
-	return s
+	return unsafe.String(&b[0], len(b))
 }

go.mod

@@ -1,5 +1,5 @@
 module github.com/godbus/dbus/v5
 
-go 1.12
+go 1.20
 
 require golang.org/x/sys v0.0.0-20220817070843-5a390386f1f2