refactor(misconf): Remove unused options

[simar7]

We have a few options within the misconfiguration scanner that aren't used they are as below:

1. combined

   trivy/pkg/iac/rego/metadata.go

   Line 225 in 39c8024

   Combined bool

2. rego warnings https://github.com/aquasecurity/trivy/blob/main/pkg/iac/scan/result.go#L198

[nikpivkin]

Warnings are used in trivy-operator tests:

grep -rn "warn"
./go.mod:360:	gopkg.in/warnings.v0 v0.1.2 // indirect
./go.sum:1799:gopkg.in/warnings.v0 v0.1.2 h1:wFXVbFY8DY5/xOe1ECiWdKCzZlxgshcYVNkBHstARME=
./go.sum:1800:gopkg.in/warnings.v0 v0.1.2/go.mod h1:jksf8JmL6Qr/oQM2OXTHunEvvTAsrWBLb6OOjuVWRNI=
./docs/docs/design/design_compliance_report.md:483:                "status": "warn"
./docs/docs/compliance/compliance.md:3:!!! warning "EXPERIMENTAL"
./docs/getting-started/installation/upgrade.md:8:!!! warning
./docs/tutorials/writing-custom-configuration-audit-policies.md:36:Once we've got our metadata defined, we need to create the logic of the policy, which is done in the `deny` or `warn`
./pkg/policy/policy_test.go:305:			name: "Should eval warn rule with invalid resource as failed check",
./pkg/policy/policy_test.go:342:		warn[res] {
./pkg/policy/policy_test.go:373:			name: "Should eval warn rule with valid resource as successful check",
./pkg/policy/policy_test.go:413:		warn[res] {
./pkg/policy/policy_test.go:555:			name:          "Should eval warn rule with any resource and multiple messages",
./pkg/policy/policy_test.go:623:			name: "Should eval warn role rule with built in policies",
./pkg/policy/policy_test.go:933:	// varMessage is the name of Rego variable used to bind deny or warn
./pkg/policy/policy_test.go:939:// `warn` rules.
./pkg/policy/policy_test.go:947:	// Messages deny or warning messages