Refresh the refernce of the closed PR when reopening (#24231)

Close #24213 
Replace #23830

#### Cause

- Before, in order to making PR can get latest commit after reopening,
the `ref`(${REPO_PATH}/refs/pull/${PR_INDEX}/head) of evrey closed PR
will be updated when pushing commits to the `head branch` of the closed
PR.

#### Changes

- For closed PR , won't perform these behavior: insert`comment`, push
`notification` (UI and email), exectue
[pushToBaseRepo](7422503341/services/pull/pull.go (L409))
function and trigger `action` any more when pushing to the `head branch`
of the closed PR.
- Refresh the reference of the PR when reopening the closed PR (**even
if the head branch has been deleted before**). Make the reference of PR
consistent with the `head branch`.

models/issues/pull_test.go

@@ -118,7 +118,7 @@ func TestHasUnmergedPullRequestsByHeadInfo(t *testing.T) {
 
 func TestGetUnmergedPullRequestsByHeadInfo(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
-	prs, err := issues_model.GetUnmergedPullRequestsByHeadInfo(1, "branch2", false)
+	prs, err := issues_model.GetUnmergedPullRequestsByHeadInfo(1, "branch2")
 	assert.NoError(t, err)
 	assert.Len(t, prs, 1)
 	for _, pr := range prs {