Add missing caption on preview checkbox

lazpaint/dialog/filter/uposterize.lfm

@@ -67,6 +67,7 @@ object FPosterize: TFPosterize
     Height = 19
     Top = 66
     Width = 130
+    Caption = 'rsPreview'
     Checked = True
     OnChange = CheckBox_PreviewChange
     State = cbChecked

lazpaint/dialog/filter/uposterize.lrj

@@ -2,6 +2,7 @@
 {"hash":179103845,"name":"tfposterize.caption","sourcebytes":[80,111,115,116,101,114,105,122,101],"value":"Posterize"},
 {"hash":214708250,"name":"tfposterize.label_levels.caption","sourcebytes":[76,101,118,101,108,115,32,58],"value":"Levels :"},
 {"hash":157433427,"name":"tfposterize.checkbox_bylightness.caption","sourcebytes":[66,121,32,108,105,103,104,116,110,101,115,115],"value":"By lightness"},
+{"hash":126662215,"name":"tfposterize.checkbox_preview.caption","sourcebytes":[114,115,80,114,101,118,105,101,119],"value":"rsPreview"},
 {"hash":497723,"name":"tfposterize.button_ok.caption","sourcebytes":[114,115,79,75],"value":"rsOK"},
 {"hash":127421996,"name":"tfposterize.button_cancel.caption","sourcebytes":[114,115,67,97,110,99,101,108],"value":"rsCancel"}
 ]}