Fix Rust doctest errors

[ohtanim]

Description of Change

Fixed the errors reported by invoking cargo test --doc --locked --release.
No functional changes are introduced - Just updated comment block in Rust code.

Before applying this PR: errors.txt

After applying this PR:

running 11 tests
test src/lib.rs - QuantumResource::resource_type (line 35) - compile ... ok
test src/lib.rs - QuantumResource::is_accessible (line 52) - compile ... ok
test src/lib.rs - QuantumResource::acquire (line 69) - compile ... ok
test src/lib.rs - QuantumResource::task_logs (line 201) - compile ... ok
test src/lib.rs - QuantumResource::release (line 85) - compile ... ok
test src/lib.rs - QuantumResource::metadata (line 234) - compile ... ok
test src/lib.rs - QuantumResource::target (line 217) - compile ... ok
test src/lib.rs - QuantumResource::task_status (line 158) - compile ... ok
test src/lib.rs - QuantumResource::task_start (line 104) - compile ... ok
test src/lib.rs - QuantumResource::task_result (line 179) - compile ... ok
test src/lib.rs - QuantumResource::task_stop (line 138) - compile ... ok

test result: ok. 11 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.38s

Checklist ✅

• Have you included a description of this change?
• Have you updated the relevant documentation to reflect this change?
• Have you made sure CI is passing before requesting a review?

Ticket

• Fixes Add makefile targets to cover all steps found in the CI and INSTALL.md #87
• Is Part of #

[OkuyanBoga]

All looks good to me, thank you very much