[nrf noup] ci: add reopen for manifest-pr action

Previously reopening of PR did not reopen manifest PR.
This commit will enable reopening of manifest PR in such case.

Signed-off-by: Kari Hamalainen <[email protected]>

Author: karhama

.github/workflows/manifest-PR.yml

@@ -1,7 +1,7 @@
 name: handle manifest PR
 on:
   pull_request_target:
-    types: [opened, synchronize, closed]
+    types: [opened, synchronize, closed, reopened]
     branches:
       - main