json: do not unescape slashes

Apparently this originated in PHP, so the json output could be directly
embedded in HTML script tags.
See https://stackoverflow.com/questions/1580647/json-why-are-forward-slashes-escaped.

Since the output of our tools is not intended directly for web page generation,
let's not do this unescaping. If needed, the consumer can always do escaping as
appropriate for the target format.

src/shared/json.c

@@ -1381,10 +1381,6 @@ static int json_format(FILE *f, JsonVariant *v, JsonFormatFlags flags, const cha
                                 fputs("\\\\", f);
                                 break;
 
-                        case '/':
-                                fputs("\\/", f);
-                                break;
-
                         case '\b':
                                 fputs("\\b", f);
                                 break;