[vsco] use '"browser": "firefox"' by default (#8127)

and re-enable TLS 1.2 cipher suites
i.e. revert c7fe6ba691

gallery_dl/extractor/vsco.py

@@ -22,7 +22,7 @@ class VscoExtractor(Extractor):
     directory_fmt = ("{category}", "{user}")
     filename_fmt = "{id}.{extension}"
     archive_fmt = "{id}"
-    tls12 = False
+    browser = "firefox"
 
     def __init__(self, match):
         Extractor.__init__(self, match)