Use Go 1.21 for golangci-lint (#26786)

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

.golangci.yml

@@ -29,7 +29,7 @@ linters:
   fast: false
 
 run:
-  go: "1.20"
+  go: "1.21"
   timeout: 10m
   skip-dirs:
     - node_modules
@@ -75,7 +75,7 @@ linters-settings:
       - name: modifies-value-receiver
   gofumpt:
     extra-rules: true
-    lang-version: "1.20"
+    lang-version: "1.21"
   depguard:
     rules:
       main: