Plot pane not staying in vsplit

[tpgillam]

As of today (having just upgraded to vscode 1.63.0), I'm finding that the plot pane does not stay in a vsplit.

Steps to reproduce:

1. Start a fresh vscode, and open the usual julia repl
2. call plot([1,2,3]) - the plot pane appears
3. Drag the plot pane into a vsplit
4. call plot([4,5,6]) the new plot appears in the plot pane, and the plot pane moves out of the split to occupy the full width of the editor again (*)

(*) More precisely, if there are multiple splits open, the plot pane will move to occupy the same split as the file in which code is being run with Execute Code in REPL and Move.

Previously, on step 4, the re-organisation wouldn't occur (and this would evidently be preferable for workflow). Not sure if this is a Julia extension bug, or VSCode bug though.

This discourse thread describes the issue too: https://discourse.julialang.org/t/vs-code-plot-pane-wont-stay-splitted/72051/3

[pfitzseb]

Fixed by #2611.