remove --all-features from test_rust.sh
After #26399 (moved), none of our crates will have any features. However, we'd like to feature-gate testing C code from Rust (#26398 (moved)) as a temporary workaround to #25386 (moved), so we need to remove the --all-features
flag. The --all-features
flags was probably a bad idea to begin with, as many crates have mutually incompatible features (e.g. curve25519-dalek
has features for different field implementation backends).