Hey there-
The only command I know of that will remove light glitches instantaneously is //fixlight, however I believe that the command is disabled on the server, or is outdated. If you mean removing light source blocks that are already there, as stated above, //replace <lightsource> 0 will replace any block (or light source block) to air. If this didn't answer your question or you have any other questions, feel free to PM me here on the forums on on Discord @ Nilly #1551.