[arm] disable strict mode for fb to json

This is a temp workaround to suppress test failures in
https://github.com/pytorch/executorch/actions/runs/12794699471/job/35670399085

Author: digantdesai

backends/arm/test/runner_utils.py

@@ -652,7 +652,6 @@ def dbg_tosa_fb_to_json(tosa_fb: bytes) -> Dict:
     cmd_flatc = [
         "flatc",
         "--json",
-        "--strict-json",
         "-o",
         tmp,
         "--raw-binary",