fix(example): go version is too low (#19293)

[bug] tutorialpb/addressbook.pb.go:317:40: predeclared any requires go1.18 or later (-lang was set to go1.14; check go.mod)

Closes #19293

COPYBARA_INTEGRATE_REVIEW=https://github.com/protocolbuffers/protobuf/pull/19293 from Kaikaikaifang:patch-2 386a337031
PiperOrigin-RevId: 698606584

examples/go/go.mod

@@ -1,5 +1,5 @@
 module github.com/protocolbuffers/protobuf/examples/go
 
-go 1.14
+go 1.18
 
 require google.golang.org/protobuf v1.27.1