Upgrade from FlatbufferString to FlatbufferSpan

Less copies, and now we can get rid of FlatbufferString

Change-Id: Ic027de4270d7232d0defadc2b193072aa8e4c8e5
diff --git a/y2020/vision/tools/python_code/BUILD b/y2020/vision/tools/python_code/BUILD
index 4ff3397..6223d76 100644
--- a/y2020/vision/tools/python_code/BUILD
+++ b/y2020/vision/tools/python_code/BUILD
@@ -49,6 +49,9 @@
     ],
     target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
+    deps = [
+        "@com_google_absl//absl/types:span",
+    ],
 )
 
 py_binary(
@@ -102,6 +105,9 @@
     ],
     target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
+    deps = [
+        "@com_google_absl//absl/types:span",
+    ],
 )
 
 cc_test(