docker: Bump base rust version to 1.74

The cargo-deny docker build was failing because rust 1.70 wasn't
sufficient. This bumps its rust version to 1.74.

Change-Id: Ica207c5b029df204d295e01486e19502691d1828
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/7159
Reviewed-by: Luke Osborne <luke@readyset.io>
Tested-by: Buildkite CI

build/Dockerfile.cargo-deny

@@ -1,3 +1,3 @@
-FROM 305232526136.dkr.ecr.us-east-2.amazonaws.com/ecr-public/docker/library/rust:1.70
+FROM 305232526136.dkr.ecr.us-east-2.amazonaws.com/ecr-public/docker/library/rust:1.74
 
 RUN cargo install cargo-deny --version 0.13.7 && cargo deny --version