completion: fix file completion of redirection targets

This fixes a regression introduced in
6fb7f9b6b - Fix completion for builtins with subcommands

src/complete.cpp

@@ -1542,6 +1542,7 @@ void completer_t::perform() {
                 tok_t prev_tok = tokens.at(tokens.size() - 2);
                 if (prev_tok.type == token_type_t::string)
                     previous_argument = prev_tok.get_source(cmd);
+                in_redirection = prev_tok.type == token_type_t::redirect;
             }
         }
 

tests/checks/complete.fish

@@ -150,3 +150,6 @@ complete -C'for _ in ' | string collect >&- && echo completed some files
 # function; #5415
 complete -C'function : --arg'
 # CHECK: --argument-names	{{.*}}
+
+complete -C'echo > /' | string length -q && echo ok
+# CHECK: ok