Bump github.com/golang-jwt/jwt to v5 (#25975)

Bumping `github.com/golang-jwt/jwt` from v4 to v5.

`github.com/golang-jwt/jwt` v5 is bringing some breaking changes:

- standard `Valid()` method on claims is removed. It's replaced by
`ClaimsValidator` interface implementing `Validator()` method instead,
which is called after standard validation. Gitea doesn't seem to be
using this logic.
- `jwt.Token` has a field `Valid`, so it's checked in `ParseToken`
function in `services/auth/source/oauth2/token.go`

---------

Co-authored-by: Giteabot <teabot@gitea.io>

routers/web/auth/oauth.go

@@ -37,7 +37,7 @@ import (
 	user_service "code.gitea.io/gitea/services/user"
 
 	"gitea.com/go-chi/binding"
-	"github.com/golang-jwt/jwt/v4"
+	"github.com/golang-jwt/jwt/v5"
 	"github.com/markbates/goth"
 	"github.com/markbates/goth/gothic"
 	go_oauth2 "golang.org/x/oauth2"
@@ -342,17 +342,15 @@ func IntrospectOAuth(ctx *context.Context) {
 	form := web.GetForm(ctx).(*forms.IntrospectTokenForm)
 	token, err := oauth2.ParseToken(form.Token, oauth2.DefaultSigningKey)
 	if err == nil {
-		if token.Valid() == nil {
-			grant, err := auth.GetOAuth2GrantByID(ctx, token.GrantID)
-			if err == nil && grant != nil {
-				app, err := auth.GetOAuth2ApplicationByID(ctx, grant.ApplicationID)
-				if err == nil && app != nil {
-					response.Active = true
-					response.Scope = grant.Scope
-					response.Issuer = setting.AppURL
-					response.Audience = []string{app.ClientID}
-					response.Subject = fmt.Sprint(grant.UserID)
-				}
+		grant, err := auth.GetOAuth2GrantByID(ctx, token.GrantID)
+		if err == nil && grant != nil {
+			app, err := auth.GetOAuth2ApplicationByID(ctx, grant.ApplicationID)
+			if err == nil && app != nil {
+				response.Active = true
+				response.Scope = grant.Scope
+				response.Issuer = setting.AppURL
+				response.Audience = []string{app.ClientID}
+				response.Subject = fmt.Sprint(grant.UserID)
 			}
 		}
 	}

routers/web/auth/oauth_test.go

@@ -13,7 +13,7 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/services/auth/source/oauth2"
 
-	"github.com/golang-jwt/jwt/v4"
+	"github.com/golang-jwt/jwt/v5"
 	"github.com/stretchr/testify/assert"
 )