Allow closing upgradeable program accounts (#19319)

sdk/program/src/loader_upgradeable_instruction.rs

@@ -117,8 +117,12 @@ pub enum UpgradeableLoaderInstruction {
     /// withdraws all the lamports
     ///
     /// # Account references
-    ///   0. `[writable]` The account to close.
+    ///   0. `[writable]` The account to close, if closing a program must be the
+    ///      ProgramData account.
     ///   1. `[writable]` The account to deposit the closed account's lamports.
-    ///   2. `[signer]` The account's authority.
+    ///   2. `[signer]` The account's authority, Optional, required for
+    ///      initialized accounts.
+    ///   3. `[writable]` The associated Program account if the account to close
+    ///      is a ProgramData account.
     Close,
 }