[BLD] Remove avx512 rustflags from Dockerfile (#5317)

## Description of changes

This PR removes avx512 rustflags from dockerfile since builds are
failing due to CI runners not supporting avx512.

it worked for CFLAGS bc those are compiler hints for optimization,
RUSTFLAGS are much more strict and require the compiling device to have
the target spec

## Test plan

_How are these changes tested?_

- [ ] Tests pass locally with `pytest` for python, `yarn test` for js,
`cargo test` for rust

## Migration plan

_Are there any migrations, or any forwards/backwards compatibility
changes needed in order to make sure this change deploys reliably?_

## Observability plan

_What is the plan to instrument and monitor this change?_

## Documentation Changes

_Are all docstrings for user-facing APIs updated if required? Do we need
to make documentation changes in the [docs
section](https://github.com/chroma-core/chroma/tree/main/docs/docs.trychroma.com)?_