[docs] Issue with missing properties in TextChannel

[Darqam]

(Killing issue template cause this is a special snowflake)

So, when looking at docs for stable and 11.4-dev, we see that .messages and .lastMessage are missing for textChannel.

After looking around it seems that anything doc related placed in textBasedChannel (https://github.com/discordjs/discord.js/blob/11.4-dev/src/structures/interfaces/TextBasedChannel.js) doesn't get pulled to the docs.

But then why is lastMessageId and lastPinTimestamp documented? Because they are re-documented on textChannel.js (https://github.com/discordjs/discord.js/blob/11.4-dev/src/structures/TextChannel.js#L38)

So I'm not sure what the best approach is for this, nor even how to fix this with docgens, but I figure knowing where the issue arises from might help.