Make pooling_test "large" to adjust timeout

Change-Id: I480f38d9ac45c8fc01bfdfda83a270cc4dd6bba9

tests/tflm/BUILD

diff --git a/tests/tflm/BUILD b/tests/tflm/BUILD
index 1b6a046..747b0e8 100644
--- a/tests/tflm/BUILD
+++ b/tests/tflm/BUILD
@@ -90,6 +90,7 @@
     srcs = [
         "@tflite-micro//tensorflow/lite/micro/kernels:pooling_test.cc",
     ],
+    hw_test_size = "large",
     deps = [
         "//crt",
         "@tflite-micro//tensorflow/lite/c:common",