test: use `T.TempDir` to create temporary test directory (#21043)

A testing cleanup. 

This pull request replaces `os.MkdirTemp` with `t.TempDir`. We can use the `T.TempDir` function from the `testing` package to create temporary directory. The directory created by `T.TempDir` is automatically removed when the test and all its subtests complete. 

This saves us at least 2 lines (error check, and cleanup) on every instance, or in some cases adds cleanup that we forgot.

Reference: https://pkg.go.dev/testing#T.TempDir

```go
func TestFoo(t *testing.T) {
	// before
	tmpDir, err := os.MkdirTemp("", "")
	require.NoError(t, err)
	defer os.RemoveAll(tmpDir)

	// now
	tmpDir := t.TempDir()
}
```

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/models/db/engine_test.go b/models/db/engine_test.go
index 41279c5005..c26d94c340 100644
--- a/models/db/engine_test.go
+++ b/models/db/engine_test.go
@@ -5,7 +5,6 @@
 package db_test
 
 import (
-	"os"
 	"path/filepath"
 	"testing"
 
@@ -20,8 +19,7 @@ import (
 func TestDumpDatabase(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
-	dir, err := os.MkdirTemp(os.TempDir(), "dump")
-	assert.NoError(t, err)
+	dir := t.TempDir()
 
 	type Version struct {
 		ID      int64 `xorm:"pk autoincr"`