"using PlotlyJS" in atreplinit() runs atreplinit() twice

It is a common practice to add "using" directives to the atreplinit() function in startup.jl. However, adding "using PlotlyJS" to this function seems to silently run atreplinit() twice, which is potentially dangerous behaviour.

The initialization seems to belong to the same REPL object, and is likely linked to adding a display when the package is read.

Example startup.jl:

```
println("startup.jl start")

atreplinit() do repl

println("atreplinit() start")

print("repl object: ");
display(repr(UInt64(pointer_from_objref(repl))))

print("length of Base.Multimedia.displays: ")
display(length(Base.Multimedia.displays))

display(stacktrace())

println("*** using PlotlyJS ***")
eval( Meta.parse( "using PlotlyJS" ) )
println("atreplinit() end")
end
println("startup.jl end")
```
output:

```
startup.jl start
startup.jl end
atreplinit() start
repl object: "0x00007f086aaa8f10"
length of Base.Multimedia.displays: 2
11-element Vector{Base.StackTraces.StackFrame}:
(::var"#1#2")(repl::REPL.LineEditREPL) at startup.jl:13
__atreplinit(repl::REPL.LineEditREPL) at client.jl:336
#invokelatest#2 at essentials.jl:708 [inlined]
invokelatest at essentials.jl:706 [inlined]
_atreplinit at client.jl:343 [inlined]
(::Base.var"#875#877"{Bool, Bool, Bool})(REPL::Module) at client.jl:386
#invokelatest#2 at essentials.jl:708 [inlined]
invokelatest at essentials.jl:706 [inlined]
run_main_repl(interactive::Bool, quiet::Bool, banner::Bool, history_file::Bool, color_set::Bool) at client.jl:372
exec_options(opts::Base.JLOptions) at client.jl:302
_start() at client.jl:485
*** using PlotlyJS ***
atreplinit() end
atreplinit() start
repl object: "0x00007f086aaa8f10"
length of Base.Multimedia.displays: 3
11-element Vector{Base.StackTraces.StackFrame}:
(::var"#1#2")(repl::REPL.LineEditREPL) at startup.jl:13
__atreplinit(repl::REPL.LineEditREPL) at client.jl:336
#invokelatest#2 at essentials.jl:708 [inlined]
invokelatest at essentials.jl:706 [inlined]
_atreplinit at client.jl:343 [inlined]
(::Base.var"#875#877"{Bool, Bool, Bool})(REPL::Module) at client.jl:386
#invokelatest#2 at essentials.jl:708 [inlined]
invokelatest at essentials.jl:706 [inlined]
run_main_repl(interactive::Bool, quiet::Bool, banner::Bool, history_file::Bool, color_set::Bool) at client.jl:372
exec_options(opts::Base.JLOptions) at client.jl:302
_start() at client.jl:485
*** using PlotlyJS ***
atreplinit() end

```

Can be reproduced in Julia 1.6.4, 1.8.2 and PlotlyJS v0.18.10.

Julia Version 1.6.4
Commit 35f0c911f4 (2021-11-19 03:54 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: AMD Ryzen 7 1700 Eight-Core Processor
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-11.0.1 (ORCJIT, znver1)

Status `~/.julia/environments/v1.6/Project.toml`
[f0f68f2c] PlotlyJS v0.18.10
[0f1e0344] WebIO v0.8.93