Sli: Generate sync providers that return iterable<array-key,TEntity>

- Further to `Sync` change in v0.99.63 (commit b232a8c), generate list
  operations that return `iterable` types with array-compatible keys

Author: lkrms

src/Toolkit/Sli/Command/Generate/GenerateSyncProvider.php

@@ -175,7 +175,7 @@ protected function run(string ...$args)
             if (SyncUtil::isListOperation($op)) {
                 $paramDoc = 'iterable<' . $service . '> $' . $camelPlural;
                 $paramCode = 'iterable $' . $camelPlural;
-                $returnDoc = 'iterable<' . $service . '>';
+                $returnDoc = 'iterable<array-key,' . $service . '>';
                 $returnCode = 'iterable';
             } else {
                 $paramDoc = $service . ' $' . $camelClass;