bug: do not format escaped quotes as in `default:"[\"a\"]"`

Go lines removes escapes as in:

```go
struct A {
a []string `yaml:"a" default:"[\"RS512\", \"RSA-OAEP\"]"`
}
```

to 

```go
struct A {
a []string `yaml:"a" default:"["RS512", "RSA-OAEP"]"`
}
```
which is wrong.

Note: You can disable formatting tags with `--no-reformat-tags`
