Add passthrough of non-Markdown docs in document trimming

[jmert]

The new extended docs feature added in #34226 defined how to trim [Julia's standard] Markdown docs. This breaks the docs retrieved in PyPlot since it just forwards through the original Python docs as plain-text (wrapped in Base.Docs.Text), and there's no appropriate trimdocs() method for that case. There is a fallback definition of the internal _trimdocs(), though, so it appears the restriction to specifically trimdocs(::Markdown.MD, ::Bool) may have been a mistake, and loosening the type on the first argument fixes the issue.

I've tested this fix on master, but it should be noted that the new v1.5 beta throws the same error when using PyPlot, so this PR should probably be backported (if accepted).

julia> using PyPlot                                                                                                                                                                                                
                                                                                                                                                                                                                   
help?> plot                                                                                                                                                                                                        
search: plot plot3D plotfile plot_date plot_trisurf plot_surface plot_wireframe triplot subplot boxplot

ERROR: MethodError: no method matching trimdocs(::Text{PyPlot.var"#1#2"{Tuple{PyPlot.LazyHelp}}}, ::Bool)
Closest candidates are:                             
  trimdocs(::Markdown.MD, ::Bool) at /home/justin/devel/ext/julia/usr/share/julia/stdlib/v1.6/REPL/src/docview.jl:111
Stacktrace:                                         
 [1] top-level scope at /home/justin/devel/ext/julia/usr/share/julia/stdlib/v1.6/REPL/src/docview.jl:366

julia> using REPL; Revise.track(REPL)

help?> plot                                         
search: plot plot3D plotfile plot_date plot_trisurf plot_surface plot_wireframe triplot subplot boxplot subplots matplotlib subplot_tool subplot2grid subplots_adjust get_plot_commands stackplot eventplot

Plot y versus x as lines and/or markers.

Call signatures::

    plot([x], y, [fmt], *, data=None, **kwargs)
    plot([x], y, [fmt], [x2], y2, [fmt2], ..., **kwargs)
[...]

[jmert]

Maybe @timholy should review since his PR added the feature?

[jmert]

bump

[tkf]

LGTM. Thanks!

[jmert]

Just another friendly bump. This would be nice to get onto the v1.5 branch.

[tkf]

I think it's fair to say this is a bug fix and backport is worth considering. So I'm adding the backport labels.

@timholy @fredrikekre It'd be great if one of you can have a look at it.