Required by the `toml` crate.

This formerly used to be the oldest version supported by the backtrace
crate, but is no longer significant.

These don't build unless you use a specially crafted lockfile.

    error: package `memchr v2.7.1` cannot be built because it requires rustc 1.61 or newer, while the currently active rustc version is 1.60.0
    error: package `addr2line v0.21.0` cannot be built because it requires rustc 1.65 or newer, while the currently active rustc version is 1.61.0
    error: package `addr2line v0.21.0` cannot be built because it requires rustc 1.65 or newer, while the currently active rustc version is 1.62.1
    error: package `addr2line v0.21.0` cannot be built because it requires rustc 1.65 or newer, while the currently active rustc version is 1.63.0
    error: package `addr2line v0.21.0` cannot be built because it requires rustc 1.65 or newer, while the currently active rustc version is 1.64.0

Remove conditional on repr(transparent)

    warning: fields `x` and `y` are never read
       --> tests/test_ensure.rs:467:13
        |
    466 |     pub struct Point {
        |                ----- fields in this struct
    467 |         pub x: i32,
        |             ^
    468 |         pub y: i32,
        |             ^
        |
        = note: `Point` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
        = note: `#[warn(dead_code)]` on by default

Apply RUSTC_WORKSPACE_WRAPPER

Debugging a recent cargo-outdated bug, it would have been nice not to
wonder whether a rustc version change in GitHub's runner image was a
contributing factor.

This reverts commit 9f84a37.

Make ensure's doc comment apply to the cfg(not(doc)) macro too