chore: allow clippy::needless_update

This lint forbids using `..Default::default()` in struct initializers
after all fields have already been initialized, but this is a useful
pattern if you know you want to add more fields to a struct in a future
PR without needing to touch a ton of initializers in unittests again
(_heavy foreshadowing_). So silence the paperclip.

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

Author: roypat

Cargo.toml

@@ -21,6 +21,7 @@ exit = "warn"
 tests_outside_test_module = "warn"
 assertions_on_result_states = "warn"
 error_impl_error = "warn"
+needless-update = "allow"
 
 [profile.dev]
 panic = "abort"