Remove fragile equal-pointers-unequal tests.
Same as https://github.com/rust-lang/rust/pull/139176
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These tests were added in #127003
These tests stop working when I change implementation details of format_args!(). These tests shouldn't rely on such implementation details.
Do these tests test anything that isn't already covered by other tests? If so, they should be expressed in a less fragile way that doesn't rely on internal details of format_args!().
cc `@GrigorenkoPV,` author of these tests.
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