[v15.0/forgejo]: chore: add modernizer linter (#11949)

**Backport: !11936**

- Go has a suite of small linters that helps with modernizing Go code by using newer functions and catching small mistakes, https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/modernize.
- Enable this linter in golangci-lint.
- There's also [`go fix`](https://go.dev/blog/gofix), which is not yet released as a linter in golangci-lint: https://github.com/golangci/golangci-lint/pull/6385

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11949
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

modules/queue/base_levelqueue_common.go

@@ -83,7 +83,7 @@ func prepareLevelDB(cfg *BaseConfig) (conn string, db *leveldb.DB, err error) {
 		}
 		conn = cfg.ConnStr
 	}
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		if db, err = nosql.GetManager().GetLevelDB(conn); err == nil {
 			break
 		}