chore: Remove ActionsRunnerRegister

- Introduced in e90db3f5cc and it was
never used and it would've never worked.

.deadcode-out

@@ -176,9 +176,6 @@ code.gitea.io/gitea/modules/markup/mdstripper
 code.gitea.io/gitea/modules/markup/orgmode
 	RenderString
 
-code.gitea.io/gitea/modules/private
-	ActionsRunnerRegister
-
 code.gitea.io/gitea/modules/process
 	Manager.ExecTimeout
 

modules/private/forgejo_actions.go

@@ -1,32 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-package private
-
-import (
-	"context"
-
-	"code.gitea.io/gitea/modules/setting"
-)
-
-type ActionsRunnerRegisterRequest struct {
-	Token   string
-	Scope   string
-	Labels  []string
-	Name    string
-	Version string
-}
-
-func ActionsRunnerRegister(ctx context.Context, token, scope string, labels []string, name, version string) (string, ResponseExtra) {
-	reqURL := setting.LocalURL + "api/internal/actions/register"
-
-	req := newInternalRequest(ctx, reqURL, "POST", ActionsRunnerRegisterRequest{
-		Token:   token,
-		Scope:   scope,
-		Labels:  labels,
-		Name:    name,
-		Version: version,
-	})
-
-	resp, extra := requestJSONResp(req, &ResponseText{})
-	return resp.Text, extra
-}