maint: add go 1.18 to CI

[vreynolds]

Which problem is this PR solving?

• go 1.18 was released earlier this month

Short description of the changes

• add 1.18 to test matrix
  • 1.18 failed ./beeline.go:177:4: fmt.Println call has possible formatting directive %s
  • removed the warning color altogether, we're not using it for any other warnings
• update default version to 1.18
• bump go orb