perf: remove unnecessary subshells in command -v checks

Replace 'if (command -v x &>/dev/null); then' with
'if command -v x &>/dev/null; then' across completion.d, rc.d and
profile.d. Parentheses forced a subshell fork for every 'if' check,
which is unnecessary overhead since command -v runs fine in the
current shell.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

rc.d/prompt

@@ -5,7 +5,7 @@
 MY_PROMPT_TOOLS="starship powerline-go"
 
 for prompt in ${MY_PROMPT_TOOLS}; do
-	if (command -v "${prompt}" &>/dev/null); then
+	if command -v "${prompt}" &>/dev/null; then
 		USE_PROMPT="${prompt}"
 		break
 	fi
@@ -15,7 +15,7 @@ case "${USE_PROMPT}" in
 
 # https://starship.rs/
 "starship")
-	if (command -v starship &>/dev/null); then
+	if command -v starship &>/dev/null; then
 		eval "$(starship init bash)"
 	else
 		echo "${USE_PROMPT} command not found"
@@ -24,7 +24,7 @@ case "${USE_PROMPT}" in
 
 # https://github.com/justjanne/powerline-go
 "powerline-go")
-	if (command -v powerline-go &>/dev/null); then
+	if command -v powerline-go &>/dev/null; then
 		function _update_ps1() {
 			PS1=$(powerline-go -jobs "$(jobs -p | wc -l)" -error $? -modules "ssh,host,wsl,user,cwd,direnv,venv,perms,git,jobs,exit,root" -modules-right "docker,docker-context,kube,terraform-workspace,termtitle" -newline)
 		}