[tune/ci] Fix GRPC resource exhausted test for tune trainables (#24467)

#24421 increased the default maximum GRPC limit to 250MB, which broke a Tune test that catches too large training functions.

This PR fixes this test by increasing the size of the experiment. However, please note that this leads to an inconsistency: For training functions of size 100 < fn < 250, an error will be raised only at runtime when trying to start the actor:

```
ValueError: The actor ImplicitFunc is too large (125 MiB > FUNCTION_SIZE_ERROR_THRESHOLD=95 MiB). Check that its definition is not implicitly capturing a large array or other object in scope. Tip: use ray.put() to put large objects in the Ray object store.
```

But it will successfully pass the registration stage `self._run_identifier = Experiment.register_if_needed(run)`.

cc @ericl should we set the default limit back to 100 MB (or maybe set the FUNCTION_SIZE_ERROR_THRESHOLD to 250 or whatever the GRPC limit is?)

python/ray/tune/tests/test_tune_restore.py

@@ -556,7 +556,7 @@ class ResourceExhaustedTest(unittest.TestCase):
         from sklearn.datasets import fetch_olivetti_faces
 
         a_large_array = []
-        for i in range(10):
+        for i in range(25):
             a_large_array.append(fetch_olivetti_faces())
 
         def training_func(config):