Remove unnecessary name qualification in docstrings

[LilithHafner]

When we give an example usage of an exported name such as

julia> Dates.lastdayofweek(DateTime("1996-01-05T12:30:00"))
1996-01-07T00:00:00

We should not qualify the name because this implies (falsely) that lastdayofweek is not exported.

Specifically, any example REPL usage of an exported symbol from a stdlib, when the example comes from a docstring defined by that stdlib, should use the unqualified name. I define "exported" to be Main.sybmol is defined and Main.symbol === Stdlib.symbol.

I made these changes with the following script:

function f()
    stdlibs = filter(readdir("stdlib")) do name
        
        # IDK how _jll's work, but I bet it makes sense to skip them.
        endswith(name, "_jll") && return false

        try
            @eval using $(Symbol(name))
            true
        catch 
            false
        end
    end

    count = 0
    for (root, _, files) in walkdir("stdlib")
        for file in files
            if endswith(file, ".jl")
                replacements = Pair{String, String}[]
                path = joinpath(root, file)

                match = "julia> "
                i = firstindex(match)
                open(path) do f
                    while !eof(f)
                        char = read(f, Char)
                        i = char == match[i] ? i + 1 : firstindex(match)
                        if i == lastindex(match) + 1
                            i = firstindex(match)
                            buff = Char[]
                            while !eof(f)
                                char = read(f, Char)
                                char == '\n' && break
                                push!(buff, char)
                            end
                            str = String(buff)
                            for stdlib in stdlibs
                                if contains(str, stdlib * '.')
                                    loc = findfirst(stdlib * '.', str)
                                    buff2 = Char[]
                                    for i in last(loc)+1:lastindex(str)
                                        char = str[i]
                                        char ∈ vcat('a':'z', 'A':'Z', '0':'9', ['_','!']) || break
                                        push!(buff2, char)
                                    end
                                    str2 = String(buff2)
                                    
                                    if isdefined(Main, Symbol(str2)) && occursin(stdlib, root) && 
                                            @eval(Main.$(Symbol(str2))) === @eval($(Symbol(stdlib)).$(Symbol(str2)))

                                        push!(replacements, "julia> " * str => "julia> " * str[begin:first(loc)-1] * str[last(loc)+1:end])
                                        count += 1
                                    end
                                end
                            end
                        end
                    end
                end

                if !isempty(replacements)
                    contents = read(path, String)
                    contents = replace(contents, replacements...)
                    write(path, contents)
                end
            end
        end
    end
    count
end
for _ in 1:3
    println(f())
end
# 77
# 16
# 0