Remove Copy impl on Ancestors

[Mark-Simulacrum]

It's probably too late to claw this back given the stabilization was ages ago in 1.28, but I was confused reading some code using it so want to see how bad it would be.

[Mark-Simulacrum]

@bors try

[rust-log-analyzer]

The job pr-check-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

     |
1638 | #[derive(Copy, Clone)]
     |          ^^^^ in this derive macro expansion
...
1641 | pub struct Utf8Ancestors<'a>(Ancestors<'a>);
     |                              ------------- this field does not implement `Copy`
     |
    --> library/core/src/marker.rs:470:0
     |
     = note: in this expansion of `#[derive(Copy)]`

[rust-bors]

☀️ Try build successful (CI)
Build commit: 8b34b7b (8b34b7b212d1b28b70125e3a9959ce3b6280fd9c, parent: 430d8297c712ca7e8a4866d7ddccf1b71ba5d4d3)

[Mark-Simulacrum]

@craterbot check

[craterbot]

👌 Experiment pr-149966 created and queued.
🤖 Automatically detected try build 8b34b7b
🔍 You can check out the queue and this experiment's details.

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