Update fog-google to 1.15.0

What does this MR do?

This updates the fog-google gem to the latest version, 1.15.0, which adds Ruby 3 support.

It is part of an ongoing effort to unblock Ruby 3 for GitLab.

fog-google contains the Ruby bindings for the Google Cloud Storage (GCS) object store API, which we use in various features.

Changelog: https://github.com/fog/fog-google/blob/master/CHANGELOG.md#changelog

1.15.0

Fixed

#534 Fix get_object not working with binary files [stanhu]

1.14.0

Added

#520 Support passing object properties to #copy_object [mshibuya]

Fixed

#530 Unescape slashes in urls [krokodaxl]

#528 Fix Ruby 3.0 kwargs error in #copy_object [deeeki]

#521 Unlink file temp file immediately [stanhu]

#527 #523 Fix Ruby 3.0 kwargs failures [stanhu]

Regression testing

Since we use object storage in many places, I was a bit nervous about this update. However, I ran a number of manual regression tests which I documented in the issue: #334030 (closed)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• [-] I have tested this MR in all supported browsers, or it's not needed.
• [-] I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #334030 (closed)