fix test_representative_config_flags_incorrectly_contain_run_args

Summary:
The test was introduced in D69508158 and never since worked on Windows.
https://www.internalfb.com/intern/test/844425130309909?ref_report_id=0
It fails with:
```
%1 is not a valid Win32 application. (os error 193)
```
This diff is fixing the test for windows.

Reviewed By: blackm00n

Differential Revision: D69793544

fbshipit-source-id: db9fc4b24677224db0df75cef630ba66b643a723

tests/core/log/test_representative_config_flags_data/prelude.bzl

@@ -6,7 +6,7 @@
 # of this source tree.
 
 def _action(ctx):
-    return [DefaultInfo(), RunInfo(ctx.attrs.src)]
+    return [DefaultInfo(), RunInfo(cmd_args("python3", ctx.attrs.src))]
 
 my_rule = rule(
     impl = _action,