docs: rust: remove unintended blockquote in Coding Guidelines

An unordered list in coding-guidelines.rst was indented, producing
a blockquote around it and making it look more indented than expected.
Remove the indentation to only output an unordered list.

Reported-by: Miguel Ojeda <ojeda@kernel.org>
Closes: https://github.com/Rust-for-Linux/linux/issues/1063


Fixes: d07479b2 ("docs: add Rust documentation")
Signed-off-by: Vincent Woltmann <vincent@woltmann.art>
Link: https://lore.kernel.org/r/20240816200339.2495875-1-vincent@woltmann.art


[ Reworded title. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>