Rust: Work around 'error[E0599]: no method named `leak` found for struct `std::string...

Rust: Work around 'error[E0599]: no method named `leak` found for struct `std::string::String` in the current scope'

Compiling with Debian GNU/Linux 12 (bookworm) packages:

    $ apt-cache madison cargo rustc
         cargo | 0.66.0+ds1-1 | http://deb.debian.org/debian bookworm/main ppc64el Packages
         cargo | 0.66.0+ds1-1 | http://deb.debian.org/debian bookworm/main Sources
         rustc | 1.63.0+dfsg1-2 | http://deb.debian.org/debian bookworm/main ppc64el Packages
         rustc | 1.63.0+dfsg1-2 | http://deb.debian.org/debian bookworm/main Sources

..., we run into:

       Compiling libformat_parser v0.1.0 ([...]/source-gcc/libgrust/libformat_parser)
    error[E0599]: no method named `leak` found for struct `std::string::String` in the current scope
       --> src/lib.rs:396:18
        |
    396 |         ptr: str.leak().as_ptr(),
        |                  ^^^^ method not found in `std::string::String`

    error[E0599]: no method named `leak` found for struct `std::string::String` in the current scope
       --> src/lib.rs:434:7
        |
    434 |     s.leak();
        |       ^^^^ method not found in `std::string::String`

    error[E0599]: no method named `leak` found for struct `std::string::String` in the current scope
       --> src/lib.rs:439:23
        |
    439 |         ptr: cloned_s.leak().as_ptr(),
        |                       ^^^^ method not found in `std::string::String`

Locally replace 1.72.0+ method 'leak' for struct 'std::string::String'.

	libgrust/
	* libformat_parser/src/lib.rs: Work around 'error[E0599]:
	no method named `leak` found for struct `std::string::String` in the current scope'.