lookup_plugins/bitwarden: ignore stderr

Otherwise we get weird JSON parsing errors:
```
An unhandled exception occurred while running the lookup plugin 'bitwarden'.
Error was a <class 'json.decoder.JSONDecodeError'>, original message:
Extra data: line 1 column 843 (char 842). Extra data: line 1 column 843 (char 842)
```

Signed-off-by: Jakub Sokołowski <jakub@status.im>

ansible/lookup_plugins/bitwarden.py

@@ -100,7 +100,7 @@ class Bitwarden(object):
         if self.session != "":
             my_env["BW_SESSION"] = self.session
         p = Popen([self.cli_path] + args, stdin=PIPE,
-                  stdout=PIPE, stderr=STDOUT, env=my_env)
+                  stdout=PIPE, stderr=PIPE, env=my_env)
         out, _ = p.communicate()
         out = out.decode()
         rc = p.wait()