Remove unused `sdk/rust/oak_tests/src/runtime.rs` (#465)
Remove unused `sdk/rust/oak_tests/src/runtime.rs` (#465)

sdk/rust/oak_tests/src/runtime.rs was previously refactored into oak/server/rust/oak_runtime/lib.rs and is no longer used.
project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak