c2rust: Use released version

Author: chrysn

riotbuild/Dockerfile

@@ -344,7 +344,7 @@ RUN \
 
 RUN \
     echo 'Installing C2Rust' >&2 && \
-    CARGO_HOME=/opt/rustup/.cargo cargo install --no-track --locked c2rust --git https://github.com/chrysn-pull-requests/c2rust --branch riscv-vector-types && \
+    CARGO_HOME=/opt/rustup/.cargo cargo install --no-track --locked c2rust --version 0.17.0 && \
     echo 'Cleaning up root-owned crates.io cache' >&2 && \
     rm -rf /opt/rustup/.cargo/{git,registry,.package-cache}