[object_store] minor bug: typos present in local variable

[Silemo]

Describe the bug

In the object_store/gcp folder, few of the files contain some minor typos.

To Reproduce

Search in the following files the respective terms:

• object_store/gcp/builder.rs :
  • signing_cedentials (it should be signing_credentials);
• object_store/gcp/client.rs :
  • repsonse (it should be response);
• object_store/gcp/credentials.rs :
  • methond (it should be method ),
  • canaonical_headers (it should be canonical_headers),
  • caninical_request (it should be canonical_request)

Expected behavior

The code works smoothly as expected, it is just written incorrectly on a grammar level.

Additional context

I just opened a PR to fix these small typos. I created the issue for clarity as requested in the PR template.

[Xuanwo]

Maybe we can introduce typos in CI.

[tustvold]

label_issue.py automatically added labels {'object-store'} from #5629