Do not run lookup index YAML with two shards (elastic#115608)

We can randomly inject a global template that defaults to 2 shards 
instead of 1. This causes the lookup index YAML tests to fail. To avoid 
this, the change requires specifying the default_shards setting for
these tests

Author: dnhatn

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/indices.create/10_basic.yml

@@ -153,7 +153,7 @@
 ---
 "Create lookup index":
   - requires:
-      test_runner_features: [ capabilities ]
+      test_runner_features: [ capabilities, default_shards ]
       capabilities:
         - method: PUT
           path: /{index}
@@ -176,7 +176,7 @@
 ---
 "Create lookup index with one shard":
   - requires:
-      test_runner_features: [ capabilities ]
+      test_runner_features: [ capabilities, default_shards ]
       capabilities:
         - method: PUT
           path: /{index}