Remove sprig's env and expandenv functions

[jake-ciolek]

Both Helm and ArgoCD remove access to these two due to security implications. It's possible to retrieve the function's pod environmental values. Some of these might be sensitive.

See more:

https://masterminds.github.io/sprig/os.html https://github.com/argoproj/argo-workflows/pull/5850 https://github.com/helm/helm/blob/e81f6140ddb22bc99a08f7409522a8dbe5338ee3/pkg/engine/funcs.go#L45

Also ran a go fmt.

Description of your changes

Fixes #67

I have:

• [x] Read and followed Crossplane's contribution process.
• [ ] Added or updated unit tests for my change.