docs: rust: quick-start: remove GDB/Binutils mention

docs: rust: quick-start: remove GDB/Binutils mention

The versions provided nowadays by even a distribution like Debian Stable
(and Debian Old Stable) are newer than those mentioned [1].

Thus remove the workaround.

Note that the minimum binutils version in the kernel is still 2.30, so
one could argue part of the note is still relevant, but it is unlikely
a kernel developer using such an old binutils is enabling Rust on a
modern kernel, especially when using distribution toolchains, e.g. the
Rust minimum version is not satisfied by Debian Old Stable.

So we are at the point where keeping the docs short and relevant for
essentially everyone is probably the better trade-off.

Link: https://packages.debian.org/search?suite=all&searchon=names&keywords=binutils
Link: https://lore.kernel.org/all/CANiq72mCpc9=2TN_zC4NeDMpFQtPXAFvyiP+gRApg2vzspPWmw@mail.gmail.com/
Reviewed-by: Tamir Duberstein <tamird@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260405235309.418950-29-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>