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, 2 insertions, 8 deletions

diff --git a/tests/integration/api_repo_file_get_test.go b/tests/integration/api_repo_file_get_test.go
index 2a7a5fa634..cca72c2b3e 100644
--- a/tests/integration/api_repo_file_get_test.go
+++ b/tests/integration/api_repo_file_get_test.go
@@ -7,11 +7,9 @@ package integration
 import (
 	"net/http"
 	"net/url"
-	"os"
 	"testing"
 
 	api "code.gitea.io/gitea/modules/structs"
-	"code.gitea.io/gitea/modules/util"
 	"code.gitea.io/gitea/tests"
 
 	"github.com/stretchr/testify/assert"
@@ -30,18 +28,14 @@ func TestAPIGetRawFileOrLFS(t *testing.T) {
 		httpContext := NewAPITestContext(t, "user2", "repo-lfs-test")
 		doAPICreateRepository(httpContext, false, func(t *testing.T, repository api.Repository) {
 			u.Path = httpContext.GitPath()
-			dstPath, err := os.MkdirTemp("", httpContext.Reponame)
-			assert.NoError(t, err)
-			defer util.RemoveAll(dstPath)
+			dstPath := t.TempDir()
 
 			u.Path = httpContext.GitPath()
 			u.User = url.UserPassword("user2", userPassword)
 
 			t.Run("Clone", doGitClone(dstPath, u))
 
-			dstPath2, err := os.MkdirTemp("", httpContext.Reponame)
-			assert.NoError(t, err)
-			defer util.RemoveAll(dstPath2)
+			dstPath2 := t.TempDir()
 
 			t.Run("Partial Clone", doPartialGitClone(dstPath2, u))