Fix error messages

[jjngx]

Proposed changes

This PR fixes issues reported by staticcheck:

➜  kubernetes-ingress git:(main) ✗ staticcheck ./internal/configs/*.go
internal/configs/annotations.go:456:28: error strings should not be capitalized (ST1005)
internal/configs/annotations.go:466:28: error strings should not be capitalized (ST1005)
internal/configs/annotations.go:501:28: error strings should not be capitalized (ST1005)
internal/configs/parsing_helpers.go:262:14: error strings should not be capitalized (ST1005)

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork