Fix staticcheck linter complains

[jjngx]

Proposed changes

This PR fixes staticcheck complains about Go error messages:

➜  kubernetes-ingress git:(fix/staticcheck-go-errors) ✗ staticcheck internal/k8s/appprotect/*.go
internal/k8s/appprotect/app_protect_configuration.go:293:74: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:402:15: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:410:15: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:418:15: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:420:14: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:602:15: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:607:15: error strings should not be capitalized (ST1005)
internal/k8s/appprotect/app_protect_configuration.go:609:14: 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