Fix Julia multiple pkg installation bug

[aaronzs]

Fix the following bug when install multiple Julia pkgs

Pkg.add("IJulia", "Example")

 => ERROR install julia packages                                                                                                                                                                            6.0s
------
 > install julia packages:
#0 0.737 ERROR: MethodError: no method matching add(::String, ::String)
#0 5.958 Closest candidates are:
#0 5.958   add(::Union{AbstractString, Pkg.Types.PackageSpec}; kwargs...) at /usr/local/julia/share/julia/stdlib/v1.8/Pkg/src/API.jl:143
#0 5.958 Stacktrace:
#0 5.958  [1] top-level scope
#0 5.958    @ none:1
------
ERRO[2022-06-28T13:50:32+08:00] failed to load docker image: Post "http://%2Fvar%2Frun%2Fdocker.sock/v1.41/images/load?quiet=1": context canceled  tag="envd-julia:dev"
error: process "/usr/local/julia/bin/julia -e using Pkg; Pkg.add(\"IJulia\", \"Example\")" did not complete successfully: exit code: 1

[gaocegege]

Thanks! I do not think the test failure is caused by the change. I will rerun it

[gaocegege]

Thanks for your contribution! 🎉 👍