`expect!` test fails after update

[lijunchen]

My env:

$ rustc --version                
rustc 1.86.0 (05f9846f8 2025-03-31)
$ cat Cargo.toml         
...
[dev-dependencies]
expect-test = "1.5.1"

Here is a mini test case to reproduce:

#[test]
fn expect_test_bug() {
    use expect_test::expect;
    expect![].assert_eq("X\n    Y\n    \nZ");
}

After run

$ env UPDATE_EXPECT=1 cargo test

This test block will be updated to

#[test]
fn expect_test_bug() {
    use expect_test::expect;
    expect![[r#"
        X
            Y
    
        Z"#]].assert_eq("X\n    Y\n    \nZ");
}

Then run cargo test, it fails because missing four spaces between Y and Z in Expect

$ cargo test
Expect:
----
X
    Y

Z
----

Actual:
----
X
    Y
    
Z
----

Diff:
----
X
    Y
    
Z
----