Cleanup protected branches when deleting users & teams (#19158) (#19174)

* Clean up protected_branches when deleting user

fixes #19094

* Clean up protected_branches when deleting teams

* fix issue

Co-authored-by: Lauris BH <lauris@nix.lv>

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/util/slice.go

@@ -0,0 +1,18 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+// RemoveIDFromList removes the given ID from the slice, if found.
+// It does not preserve order, and assumes the ID is unique.
+func RemoveIDFromList(list []int64, id int64) ([]int64, bool) {
+	n := len(list) - 1
+	for i, item := range list {
+		if item == id {
+			list[i] = list[n]
+			return list[:n], true
+		}
+	}
+	return list, false
+}