Linux: Remove --nodetach option for xsel copy. (#35180)

The `--nodetach` option causes `clipboard(x)` to hang indefinitely on (most? All which I have tried) linux systems. Removing this option fixes `clipboard(x)`, but briefly spawns a child process. Since `clipboard(x)` is designed for interactive use, this shouldn't be an issue.

stdlib/InteractiveUtils/src/clipboard.jl

@@ -34,7 +34,7 @@ elseif Sys.islinux() || Sys.KERNEL === :FreeBSD
     _clipboardcmd = nothing
     const _clipboard_copy = Dict(
             :xsel  => Sys.islinux() ?
-                `xsel --nodetach --input --clipboard` :
+                `xsel --input --clipboard` :
                 `xsel -c`,
             :xclip => `xclip -silent -in -selection clipboard`,
         )