gccrs: Fix translation mistakes 2023 in GCC/Rust [PR108890]

gccrs: Fix translation mistakes 2023 in GCC/Rust [PR108890]

In https://gcc.gnu.org/PR108890 "Translation mistakes 2023"
@rillig lists several issues with GCC/Rust diagnostics and
option help texts (but also a few non-GCC/Rust).

This commit fix mistakes only related to GCC/Rust,
specifically to the file `gcc/rust/lang.opt`.

closes https://github.com/Rust-GCC/gccrs/issues/1916

	PR translation/108890
	gcc/rust/
	* lang.opt: Fix translation mistakes 2023 in
	GCC/Rust [PR108890]
	(line 67): change the inconsistent tab to spaces
	(line 75): wrap bare placeholder `integer`
	(line 79): remove redundant text of `Choose which`
	(line 96): remove redundant text of `Choose which`
	(line 112): remove redundant `Flag to`
	(line 124): correct the exclusive term `When to stop`
	(line 124): correct typo of `copimlation`

Signed-off-by: Tieway59 <tieway59@foxmail.com>