Track MSRV 1.85 Lingering Issues

[landonxjames]

Grep the code for TODO(MSRV1.85 follow-up) to find these:

• In Dockerfile remove some allowed lints. One of these will be fixed by Fix redundant closure warnings in Rust 1.82 #4125 and the other will likely be fixed by Upgrade pyo3 and pyo3-async-runtimes to version 0.25 #4152
• Weird setup in check-aws-sdk-standalone-integration-tests: There is a comment in the file explaining what is going on, but the gist of it is that it seems like the RUSTFLAGS in our Dockerfile were overriding the cfg flag set in .cargo/config.toml.