cleantests/ui/assign_ops.rs

When all //~ were removed from tests, these were replaced with empty
lines to leave the numbers in the expected stderr untouched.

Cleaning the empty lines for clarity.

If there is interest, I could slowly do the rest of the test files that have weird looking empty files. Happy to do so :smile:, the clone() lint I have assigned is taking me a bit more time of research.

该提问来源于开源项目：rust-lang/rust-clippy