🐛 Update dockerfile

[genevieveluyt]

Description

As a result of recent changes which require Go 1.16 (namely, embed), the Dockerfile no longer works because it's using an older version of Go. Go release builds the binary locally and then copies it into the image so we didn't notice it before.

Fixes #338

Type of change

• Bug fix 🐛
• New feature ✨
• This change requires a documentation update 📖
• Breaking changes ⚠️

How Has This Been Tested?

• docker build -t kubeaudit .

Checklist:

• I have 🎩 my changes (A 🎩 specifically includes pulling down changes, setting them up, and manually testing the changed features and potential side effects to make sure nothing is broken)
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• The test coverage did not decrease

[dani-santos-code]

thanks for the quick fix!