Fix #3444/#4774, get_json_document over JSON.parse

Forgot to update these when I wrote new modules.

modules/auxiliary/scanner/http/chromecast_webserver.rb

@@ -37,12 +37,7 @@ class MetasploitModule < Msf::Auxiliary
 
     return unless (res && res.code == 200)
 
-    begin
-      json = JSON.parse(res.body)
-    rescue JSON::ParserError
-      return
-    end
-
+    json = res.get_json_document
     name, ssid = json['name'], json['ssid']
 
     if name && ssid

modules/auxiliary/scanner/http/chromecast_wifi.rb

@@ -43,7 +43,7 @@ class MetasploitModule < Msf::Auxiliary
       'SortIndex' => -1
     )
 
-    JSON.parse(res.body).each do |wap|
+    res.get_json_document.each do |wap|
       waps_table << [
         wap['bssid'],
         wap['signal_level'],