fix: Don't complete _command on zsh (#1690)

Previously the generated zsh completion script started with the line

    #compdef _<command> <command>

where <command> is the command that the zsh completion script is
generated for.

This enabled completions for both <command> and _<command>, but
_<command> is the completion function itself and should not be
completed. Furthermore, attempting to autocomplete _<command> (e.g.
typing "_<command><Space><Tab>" in a zsh shell) causes zsh to hang.

This commit fixes the #compdef line to only complete <command>, not
_<command>.

Co-authored-by: Arvid Norlander <VorpalBlade@users.noreply.github.com>

zsh_completions.go

@@ -75,7 +75,7 @@ func genZshComp(buf io.StringWriter, name string, includeDesc bool) {
 	if !includeDesc {
 		compCmd = ShellCompNoDescRequestCmd
 	}
-	WriteStringAndCheck(buf, fmt.Sprintf(`#compdef _%[1]s %[1]s
+	WriteStringAndCheck(buf, fmt.Sprintf(`#compdef %[1]s
 
 # zsh completion for %-36[1]s -*- shell-script -*-