[BE] f-stringify torch/ and scripts (#105538)

This PR is a follow up on the pyupgrade series to convert more strings to use f-strings using `flynt`.

- https://docs.python.org/3/reference/lexical_analysis.html#f-strings
- https://pypi.org/project/flynt/

Command used:

```
flynt torch/ -ll 120
flynt scripts/ -ll 120
flynt tools/ -ll 120
```

and excluded `collect_env.py`

Pull Request resolved: https://github.com/pytorch/pytorch/pull/105538
Approved by: https://github.com/ezyang, https://github.com/malfet

torch/jit/_shape_functions.py

@@ -37,8 +37,7 @@ def broadcast(a: List[int], b: List[int]):
         if sizeA != sizeB and sizeA != 1 and sizeB != 1:
             # TODO: only assertion error is bound in C++ compilation right now
             raise AssertionError(
-                "The size of tensor a {} must match the size of tensor b ("
-                "{}) at non-singleton dimension {}".format(sizeA, sizeB, i)
+                f"The size of tensor a {sizeA} must match the size of tensor b ({sizeB}) at non-singleton dimension {i}"
             )
 
         expandedSizes.append(sizeB if sizeA == 1 else sizeA)
@@ -81,8 +80,7 @@ def broadcast_inplace(a: List[int], b: List[int]):
     dimsB = len(b)
     if dimsB > dimsA:
         raise AssertionError(
-            "The dims of tensor b ({}) must be less than or equal to"
-            "the dims of tensor a ({}) ".format(dimsB, dimsA)
+            f"The dims of tensor b ({dimsB}) must be less than or equal tothe dims of tensor a ({dimsA}) "
         )
     for dimA in range(dimsA):
         dimB = dimsB - dimsA + dimA