Clean up some unused variables.

This is essentially 1ccc0c8c1a without the renames and some other things related to Psalm.

update.php

@@ -188,7 +188,6 @@
 	Debug::log("Lock: $lock_filename");
 
 	$lock_handle = make_lockfile($lock_filename);
-	$must_exit = false;
 
 	if (isset($options["task"]) && isset($options["pidlock"])) {
 		$waits = $options["task"] * 5;
@@ -512,8 +511,6 @@
 			exit(1);
 		}
 
-		$rc = -1;
-
 		if ($enable) {
 			Debug::log("Enabling API access for user $login...");
 			$rc = Prefs::set(Prefs::ENABLE_API_ACCESS, true, $uid, null);