chore: security updates

[mitchnielsen]

Security updates, including Golang -> 1.21 and updating the net package (which was reverted in #271 for issues related to glibc, which have already been addressed in the Dockerfile changes here).

Scanning

$ docker save sloop:9f71715 -o sloop_9f71715.tar

$ ocker run --rm -v /Users/mitch/code/github.com/prefecthq/platform/main/sloop_9f71715.tar:/tmp/sloop_9f71715.tar ghcr.io/aquasecurity/trivy:0.52.2 image --input /tmp/sloop_9f71715.tar --ignore-unfixed=true --scanners=vuln --severity=HIGH,CRITICAL --no-progress
2024-07-02T17:18:09Z    INFO    Need to update DB
2024-07-02T17:18:09Z    INFO    Downloading DB...       repository="ghcr.io/aquasecurity/trivy-db:2"
2024-07-02T17:18:36Z    INFO    Vulnerability scanning is enabled
2024-07-02T17:18:36Z    INFO    Detected OS     family="debian" version="12.5"
2024-07-02T17:18:36Z    INFO    [debian] Detecting vulnerabilities...   os_version="12" pkg_num=5
2024-07-02T17:18:36Z    INFO    Number of language-specific files       num=1
2024-07-02T17:18:36Z    INFO    [gobinary] Detecting vulnerabilities...

/tmp/sloop_9f71715.tar (debian 12.5)
====================================
Total: 0 (HIGH: 0, CRITICAL: 0)

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @mitchnielsen to sign the Salesforce Inc. Contributor License Agreement.

[mitchnielsen]

Meant to open this in my fork since this repository doesn't appear to be actively maintained at the moment.