Update rust version in forc docker image (#6422)

## Description
Minor non-critical-path fix for the forc docker image which is rarely
used but causing CI pipeline alerts due to being on an out of date
version of Rust.

Co-authored-by: Joshua Batty <joshpbatty@gmail.com>

deployment/Dockerfile

@@ -1,5 +1,5 @@
 # Stage 1: Build
-FROM lukemathwalker/cargo-chef:latest-rust-1.76 as chef
+FROM lukemathwalker/cargo-chef:latest-rust-1.79 as chef
 WORKDIR /build/
 # hadolint ignore=DL3008
 RUN apt-get update && \