Rename Sync2 -> Sync (#26479)

The xorm `Sync2` has already been deprecated in favor of `Sync`,
so let's do the same inside the Gitea codebase.

Command used to replace everything:
```sh
for i in $(ag Sync2 --files-with-matches); do vim $i -c ':%sno/Sync2/Sync/g' -c ':wq'; done
```

models/migrations/v1_9/v83.go

@@ -23,5 +23,5 @@ func AddUploaderIDForAttachment(x *xorm.Engine) error {
 		CreatedUnix   timeutil.TimeStamp `xorm:"created"`
 	}
 
-	return x.Sync2(new(Attachment))
+	return x.Sync(new(Attachment))
 }

models/migrations/v1_9/v84.go

@@ -13,5 +13,5 @@ func AddGPGKeyImport(x *xorm.Engine) error {
 		Content string `xorm:"TEXT NOT NULL"`
 	}
 
-	return x.Sync2(new(GPGKeyImport))
+	return x.Sync(new(GPGKeyImport))
 }

models/migrations/v1_9/v85.go

@@ -40,8 +40,8 @@ func HashAppToken(x *xorm.Engine) error {
 		return err
 	}
 
-	if err := sess.Sync2(new(AccessToken)); err != nil {
-		return fmt.Errorf("Sync2: %w", err)
+	if err := sess.Sync(new(AccessToken)); err != nil {
+		return fmt.Errorf("Sync: %w", err)
 	}
 
 	if err := sess.Commit(); err != nil {
@@ -112,8 +112,8 @@ func resyncHashAppTokenWithUniqueHash(x *xorm.Engine) error {
 	if err := sess.Begin(); err != nil {
 		return err
 	}
-	if err := sess.Sync2(new(AccessToken)); err != nil {
-		return fmt.Errorf("Sync2: %w", err)
+	if err := sess.Sync(new(AccessToken)); err != nil {
+		return fmt.Errorf("Sync: %w", err)
 	}
 	return sess.Commit()
 }

models/migrations/v1_9/v86.go

@@ -12,5 +12,5 @@ func AddHTTPMethodToWebhook(x *xorm.Engine) error {
 		HTTPMethod string `xorm:"http_method DEFAULT 'POST'"`
 	}
 
-	return x.Sync2(new(Webhook))
+	return x.Sync(new(Webhook))
 }

models/migrations/v1_9/v87.go

@@ -13,5 +13,5 @@ func AddAvatarFieldToRepository(x *xorm.Engine) error {
 		Avatar string `xorm:"VARCHAR(64)"`
 	}
 
-	return x.Sync2(new(Repository))
+	return x.Sync(new(Repository))
 }