test_lines_option_max_u16_no_overflow intermittent failure

---- test_more::test_lines_option_max_u16_no_overflow stdout ----
bin: "/Users/runner/work/coreutils/coreutils/target/aarch64-apple-darwin/debug/coreutils"
write(default): /var/folders/df/djsxfhc17x95674wsm_g8s980000gn/T/.tmpgBnQ4J/test.txt
run: /Users/runner/work/coreutils/coreutils/target/aarch64-apple-darwin/debug/coreutils more -n 65535 test.txt

thread 'test_more::test_lines_option_max_u16_no_overflow' panicked at tests/by-util/test_more.rs:270:5:
assertion failed: output.contains("line1")
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/panicking.rs:75:14
   2: core::panicking::panic
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/panicking.rs:145:5
   3: tests::test_more::test_lines_option_max_u16_no_overflow
             at ./tests/by-util/test_more.rs:270:5
   4: tests::test_more::test_lines_option_max_u16_no_overflow::{{closure}}
             at ./tests/by-util/test_more.rs:264:43
   5: core::ops::function::FnOnce::call_once
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/ops/function.rs:250:5
   6: core::ops::function::FnOnce::call_once
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

https://github.com/uutils/coreutils/actions/runs/33248246244/job/99090102438?pr=14166

Start with tests/by-util/test_more.rs, especially test_lines_option_max_u16_no_overflow around line 270, and reproduce the command from the failure log. Compare intermittent output against the assertion that expects "line1", including the linked CI run if needed. Done means the test is reliable and passes for the reported max-u16 case.