Rollup merge of #140576 - m-ou-se:fragile-tests, r=compiler-errors

Remove fragile equal-pointers-unequal tests.

Same as #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.

Author: matthiaskrgr