docs: fix connection pool size for samples (#880)

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Fixes #<issue_number_goes_here> ☕️

samples/snippets/src/main/java/com/example/bigtable/ConfigureConnectionPool.java

@@ -37,7 +37,7 @@ public static void configureConnectionPool(String projectId, String instanceId)
     settingsBuilder.stubSettings()
         .setTransportChannelProvider(
             EnhancedBigtableStubSettings.defaultGrpcTransportProviderBuilder()
-                .setPoolSize(250)
+                .setPoolSize(10)
                 .build());
 
     BigtableDataSettings settings = settingsBuilder.build();

samples/snippets/src/test/java/com/example/bigtable/ConfigureConnectionPoolTest.java

@@ -41,6 +41,6 @@ public void testConfigureConnectionPool() {
     ConfigureConnectionPool.configureConnectionPool(projectId, instanceId);
 
     String output = bout.toString();
-    assertThat(output, CoreMatchers.containsString("Connected with pool size of 250"));
+    assertThat(output, CoreMatchers.containsString("Connected with pool size of 10"));
   }
 }