Update bash syntax for auto-complete (#29808)

Per #27828.

Author: SeanKilleen

docs/core/tools/enable-tab-autocomplete.md

@@ -61,17 +61,14 @@ To add tab completion to your **bash** shell for the .NET CLI, add the following
 ```bash
 # bash parameter completion for the dotnet CLI
 
-_dotnet_bash_complete()
+function _dotnet_bash_complete()
 {
-  local word=${COMP_WORDS[COMP_CWORD]}
+  local cur="${COMP_WORDS[COMP_CWORD]}" IFS=$'\n'
+  local candidates
 
-  local completions
-  completions="$(dotnet complete --position "${COMP_POINT}" "${COMP_LINE}" 2>/dev/null)"
-  if [ $? -ne 0 ]; then
-    completions=""
-  fi
+  read -d '' -ra candidates < <(dotnet complete --position "${COMP_POINT}" "${COMP_LINE}" 2>/dev/null)
 
-  COMPREPLY=( $(compgen -W "$completions" -- "$word") )
+  read -d '' -ra COMPREPLY < <(compgen -W "${candidates[*]:-}" -- "$cur")
 }
 
 complete -f -F _dotnet_bash_complete dotnet