Function: remove_tag

--Usage--
> remove_tag(tag: some_tag, some_string)

Remove a tag and its matching close tag from a [[type:tagged string]], but keep the contents.

The tag can be a whole tag, @"<tag>"@, or a prefix @"<i"@. In the latter case all tags starting with @"<i"@ are removed.

--Parameters--
! Parameter	Type			Description
| @tag@		[[type:string]]		Tag to remove
| @input@	[[type:tagged string]]	String to remove tags from

--Examples--
> remove_tag(tag: "<b>", "<b>bold <i>text</i></b>")  ==  "bold <i>text</i>"
> remove_tag(tag: "<b", "<b-auto>bold</b-auto> text")  ==  "bold text"
>
> f := remove_tag@(tag: "<i-auto>")
> f("text, <i-auto>reminder</i-auto> <i>italic</i>") == "text, reminder <i>italic</i>"

--See also--
| [[fun:tag_contents]]		Change the contents of a specific tag.
| [[fun:remove_tags]]		Remove all tags from tagged text.
| [[fun:to_text]]		Remove all tags from tagged text, and convert it to a [[type:string]].
