RUBY-3372 Fix failing explain tests (#2782)

Author: comandeo-mongo

spec/mongo/collection/view/aggregation_spec.rb

@@ -321,7 +321,12 @@
           min_server_fcv '4.2'
 
           let(:result) do
-            aggregation.explain['queryPlanner']['collation']['locale']
+            if aggregation.explain.key?('queryPlanner')
+              aggregation.explain['queryPlanner']['collation']['locale']
+            else
+              # 7.2+ sharded cluster
+              aggregation.explain['shards'].first.last['queryPlanner']['collation']['locale']
+            end
           end
 
           it_behaves_like 'applies the collation'