Clean up deprecated PreTeXt

[siwelwerd]

While looking into #487 last night, I noticed some PTX:WARNINGs that we should clean up

warning: * PTX:DEPRECATE: (2017-08-04) the "task" element is no longer used as a child of a top-level division, but is instead being used to divide the other "project-like" elements.  It can be replaced by a functional equivalent: "project", "activity", "exploration", or "investigation" (2 times)
*              located within: "Sample Problem and Solution" (title)
*              located within: "Sample Problem and Solution" (title)
* --------------
warning: * PTX:DEPRECATE: (2024-10-08) elements previously included in a "titlepage" element inside the "frontmatter" (author, editor, credit, date, and event) should now be placed in "frontmatter/bibinfo".  To ensure a title page is created, put only the empty element "titlepage-items" inside "titlepage".  Until you move these elements, we will try to honor your intent. (1 time)
*              located within: "frontmatter" (xml:id)
* --------------
warning: * PTX:DEPRECATE: (2024-10-08) elements previously included in a "colophon" element inside the "frontmatter" (credit, copyright, edition, and website) should now be placed in "frontmatter/bibinfo". To produce a "colophon", include only the empty element "colophon-items" inside "colophon" Until you move these elements, we will try to honor your intent. (1 time)
*              located within: "colophon" (xml:id)
* --------------
warning: * PTX:DEPRECATE: (2024-11-19) program/input now should be program/code. An automatic correction will be attempted. (1 time)
*              located within: "LE2-rref-tech" (xml:id)
* --------------

[siwelwerd]

@StevenClontz Is part of this this related to #463, which I thought you fixed?

[StevenClontz]

Sort of, it's other deprecations between 2.6.x and 2.10.x we need to tidy up.

[siwelwerd]

I'm not seeing any more warnings when I build, so assuming these were all taken care of. Can reopen if that's not the case.