fix(react-rust-postgres): change server image base

[jdrouet]

closes #149

use rust 1.xx debian based image instead of nightly

[jdrouet]

@glours PTAL 😉

[glours]

Thanks @jdrouet 🙏
I got this issue when doing a docker compose up

backend_1   | error: failed to run custom build command for `pear_codegen v0.1.4`
backend_1   |
backend_1   | Caused by:
backend_1   |   process didn't exit successfully: `/code/target/debug/build/pear_codegen-3e77a9c961659f3c/build-script-build` (exit status: 101)
backend_1   |   --- stderr
backend_1   |   Error: Pear requires a 'dev' or 'nightly' version of rustc.
backend_1   |   Installed version: 1.53.0 (2021-06-17)
backend_1   |   Minimum required:  1.31.0-nightly (2018-10-05)
backend_1   |   thread 'main' panicked at 'Aborting compilation due to incompatible compiler.', /usr/local/cargo/registry/src/github.com-1ecc6299db9ec823/pear_codegen-0.1.4/build.rs:24:13
backend_1   |   note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
backend_1   | warning: build failed, waiting for other jobs to finish...
backend_1   | error: build failed
backend_1 exited with code 101

[jdrouet]

I'll take a look tonight. I'll probably replace rocket by actix-web that doesn't require rust nightly.