[CI] Fix flake8 rule E225: Missing whitespace around operator (#48188)

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## Why are these changes needed?

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solves. -->
See #47991 
When running the following `flake8` command to check for errors:
```
flake8 --select E225 --extend-exclude python/ray/core/generated,python/ray/serve/generated/,python/ray/cloudpickle/,python/ray/_private/runtime_env/_clonevirtualenv.py,doc/external/,python/ray/dashboard/client/node_modules
```
the following error occurs : 

![image](https://github.com/user-attachments/assets/e595a58e-677d-480f-9490-f52e62e4f0cf)



## Related issue number
Closes #48059 
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## Checks

- [x] I've signed off every commit(by using the -s flag, i.e., `git
commit -s`) in this PR.
- [x] I've run `scripts/format.sh` to lint the changes in this PR.
- [ ] I've included any doc changes needed for
https://docs.ray.io/en/master/.
- [ ] I've added any new APIs to the API Reference. For example, if I
added a
method in Tune, I've added it in `doc/source/tune/api/` under the
           corresponding `.rst` file.
- [ ] I've made sure the tests are passing. Note that there might be a
few flaky tests, see the recent failures at https://flakey-tests.ray.io/
- Testing Strategy
   - [ ] Unit tests
   - [ ] Release tests
   - [ ] This PR is not tested :(

Signed-off-by: LeoLiao123 <[email protected]>

release/air_tests/air_benchmarks/mlperf-train/resnet50_ray_air.py

@@ -529,7 +529,7 @@ def append_to_test_output_json(path, metrics):
     available_disk_space = statvfs.f_bavail * statvfs.f_frsize
     expected_disk_usage = args.num_images_per_epoch * APPROX_PREPROCESS_IMAGE_BYTES
     print(f"Available disk space: {available_disk_space / 1e9}GB")
-    print(f"Expected disk usage: {expected_disk_usage/ 1e9}GB")
+    print(f"Expected disk usage: {expected_disk_usage / 1e9}GB")
     disk_error_expected = expected_disk_usage > available_disk_space * 0.8
 
     datasets = {}

release/nightly_tests/stress_tests/test_placement_group.py

@@ -186,7 +186,7 @@ def pg_launcher(pre_created_pgs, num_pgs_to_create):
     )
     print(
         "Avg placement group removing time: "
-        f"{total_removing_time / total_trial* 1000} ms"
+        f"{total_removing_time / total_trial * 1000} ms"
     )
     print("PASSED.")