Remove unnecessary read_config on sanitizer

Summary: This read_config to set nosan modifier was necessary because the fbcode modefiles didn't inject modifiers. Now they do, so now we can remove this read_config

Reviewed By: IanChilds

Differential Revision: D67432138

fbshipit-source-id: d2f95a9b5a5e831d057064ec56dc0a3ee5b9cb3f

app/modifier.bzl

@@ -63,13 +63,7 @@ def buck2_modifiers():
             "ovr_config//build_mode/default_opt_cxx:enabled": (
                 "ovr_config//build_mode:no-san"
             ),
-            # Unfortunately, setting `ovr_config//build_mode:no-san` like this is a bit problematic when using sanitizer
-            # modefiles because the no-san value here would override the sanitizer constraint set by those modefiles
-            # in the target platform, meaning we would always get sanitizer disabled no matter what sanitizer modefile
-            # is used. To work around this, explicitly check that we are not using any sanitizer modefile by checking
-            # that the `fbcode.sanitizer` buckconfig is set to the default value "address-undefined-dev". We can undo this
-            # change in the future when our CI is updated to use sanitizer modifiers instead of sanitizer modefiles.
-        }) if read_config("fbcode", "sanitizer") == "address-undefined-dev" else None,
+        }),
         modifiers.conditional({
             "DEFAULT": None,
             "ovr_config//build_mode/default_opt_cxx:enabled": modifiers.conditional({