revert: keep narrow RedisException catch on lock acquire

Reverts the catch widening from earlier — the underlying
Utopia\Lock\Distributed::tryAcquire only calls ext-redis methods,
which throw RedisException exclusively. Catching Throwable was
over-broad and would silently swallow real bugs (TypeError, Error)
into a fail-open path.

src/Appwrite/Locking/Lock.php

@@ -129,7 +129,7 @@ final class Lock
 
         try {
             $acquired = $orFail ? $lock->acquire($waitTimeout) : $lock->tryAcquire();
-        } catch (Throwable $e) {
+        } catch (\RedisException $e) {
             $this->attempts->add(1, ['outcome' => 'backend_error', ...$labels]);
             $this->reportError('backend_error', $key, $target, $e);