Update snapshot

It turns out the test wasn't broken, I had just flubbed the escaping in
the snapshot. The easiest way to see that this actually works is

```bash
$ cat | prettier --stdin
"hol\\a (the a is not escaped)" // press Control-D after the newline
"hol\\a (the a is not escaped)"; // press Control-D after the newline
```

tests/quotes/__snapshots__/jsfmt.spec.js.snap

@@ -150,8 +150,8 @@ exports[`strings.js 1`] = `
 "a";
 "hola";
 "hola";
-"hol\\a (the a is not escaped)";
-"hol\\a (the a is not escaped)";
+"hol\\\\a (the a is not escaped)";
+"hol\\\\a (the a is not escaped)";
 "multiple a unnecessary a escapes";
 "multiple a unnecessary a escapes";
 "unnecessarily escaped character preceded by escaped backslash \\\\a";
@@ -311,8 +311,8 @@ exports[`strings.js 2`] = `
 'a';
 'hola';
 'hola';
-'hol\\a (the a is not escaped)';
-'hol\\a (the a is not escaped)';
+'hol\\\\a (the a is not escaped)';
+'hol\\\\a (the a is not escaped)';
 'multiple a unnecessary a escapes';
 'multiple a unnecessary a escapes';
 'unnecessarily escaped character preceded by escaped backslash \\\\a';