[BE] fix ruff rule E226: add missing whitespace around operator in f-strings (#144415)

The fixes are generated by:

```bash
ruff check --fix --preview --unsafe-fixes --select=E226 .
lintrunner -a --take "RUFF,PYFMT" --all-files
```

Pull Request resolved: https://github.com/pytorch/pytorch/pull/144415
Approved by: https://github.com/huydhn, https://github.com/Skylion007

torch/_dynamo/debug_utils.py

@@ -203,7 +203,9 @@ class NNModuleToString:
                 )
             if buffer.is_cuda:
                 tensor_str = f"{tensor_str}.cuda()"
-            model_str += f"{tab*2}self.register_buffer('{buffer_name}', {tensor_str})\n"
+            model_str += (
+                f"{tab * 2}self.register_buffer('{buffer_name}', {tensor_str})\n"
+            )
 
         for param_name, param in gm._parameters.items():
             if param is None:

torch/_numpy/testing/utils.py

@@ -2288,9 +2288,7 @@ def check_free_memory(free_bytes):
             )
             mem_free = -1
         else:
-            msg = (
-                f"{free_bytes/1e9} GB memory required, but {mem_free/1e9} GB available"
-            )
+            msg = f"{free_bytes / 1e9} GB memory required, but {mem_free / 1e9} GB available"
 
     return msg if mem_free < free_bytes else None
 

torch/distributed/tensor/examples/convnext_example.py

@@ -243,13 +243,16 @@ def train_convnext_example():
     max_reserved = torch.cuda.max_memory_reserved()
     max_allocated = torch.cuda.max_memory_allocated()
     print(
-        f"rank {rank}, {ITER_TIME} iterations, average latency {(end - start)/ITER_TIME*1000:10.2f} ms"
+        f"rank {rank}, {ITER_TIME} iterations, "
+        f"average latency {(end - start) / ITER_TIME * 1000:10.2f} ms"
     )
     print(
-        f"rank {rank}, forward {forward_time/ITER_TIME*1000:10.2f} ms, backward {backward_time/ITER_TIME*1000:10.2f} ms"
+        f"rank {rank}, forward {forward_time / ITER_TIME * 1000:10.2f} ms, "
+        f"backward {backward_time / ITER_TIME * 1000:10.2f} ms"
     )
     print(
-        f"rank {rank}, max reserved {max_reserved/1024/1024/1024:8.2f} GiB, max allocated {max_allocated/1024/1024/1024:8.2f} GiB"
+        f"rank {rank}, max reserved {max_reserved / 1024 / 1024 / 1024:8.2f} GiB, "
+        f"max allocated {max_allocated / 1024 / 1024 / 1024:8.2f} GiB"
     )
     dist.destroy_process_group()