Refresh stale file handles for REPL history.

[marmarelis]

Often, when running multiple Julia REPLs on a Linux cluster with network-mounted home directories, the REPL's history file handle becomes stale and each new line errors out with the following:

┌ Error: Error in the keymap
│   exception =
│    SystemError: seekend: Stale file handle
│    Stacktrace:
│      [1] systemerror(p::String, errno::Int32; extrainfo::Nothing)
│        @ Base ./error.jl:168
│      [2] #systemerror#62
│        @ ./error.jl:167 [inlined]
│      [3] systemerror
│        @ ./error.jl:167 [inlined]
│      [4] seekend(s::IOStream)
│        @ Base ./iostream.jl:163
│      [5] add_history(hist::REPL.REPLHistoryProvider, s::REPL.LineEdit.PromptState)
│        @ REPL /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPL.jl:562
│      [6] add_history(s::REPL.LineEdit.PromptState)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:1248
│      [7] add_history(::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:227
│      [8] commit_line(s::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2081
│      [9] (::REPL.LineEdit.var"#110#163")(::REPL.LineEdit.MIState, ::Any, ::Vararg{Any, N} where N)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2163
│     [10] #invokelatest#2
│        @ ./essentials.jl:708 [inlined]
│     [11] invokelatest
│        @ ./essentials.jl:706 [inlined]
│     [12] (::REPL.LineEdit.var"#22#23"{REPL.LineEdit.var"#110#163", String})(s::Any, p::Any)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:1414
│     [13] prompt!(term::REPL.Terminals.TextTerminal, prompt::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2534
│     [14] run_interface(terminal::REPL.Terminals.TextTerminal, m::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2436
│     [15] run_frontend(repl::REPL.LineEditREPL, backend::REPL.REPLBackendRef)
│        @ REPL /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPL.jl:1126
│     [16] (::REPL.var"#44#49"{REPL.LineEditREPL, REPL.REPLBackendRef})()
│        @ REPL ./task.jl:406
└ @ REPL.LineEdit /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2536

I introduced a small fix to attempt reopening the file after a SystemError, thus refreshing the handle. This is my first time contributing so all feedback is welcome.