Cache doesn't work with AWS S3 if using FIPS endpoints

When using AWS S3 FIPS endpoints, cache operations fail.

For example, when using the following cache configuration for runner

[runners.cache]
Type = "s3"
Shared = true
[runners.cache.s3]
  ServerAddress = "s3-fips.us-east-1.amazonaws.com"
  AccessKey = "<AWS_ACCESS_KEY_ID>"
  SecretKey = "<AWS_SECRET_ACCESS_KEY>"
  BucketName = "foobar-bucket"
  BucketLocation = "us-east-1"

We see logs similar to the following

Saving cache for successful job
Creating cache test-cache-1-protected...
test_file: found 1 matching files and directories  
Uploading cache.zip to https://foobar-bucket.s3-fips.us-east-1.amazonaws.com/project/36878543/test-cache-1-protected 
FATAL: received: 400 Bad Request                   
Failed to create cache

On debugging more, we find that the presigned URL used by cache-archiver, when visited via browser shows the following error message

Error parsing the X-Amz-Credential parameter; the region 'fips.us-east-1' is wrong; expecting 'us-east-1'

On investigating more, found that this actually stems from the underlying minio-go library. Opened an issue and a PR upstream. The PR has been merged, so it should be fixed in the next version of the library. When that is out, we should bump our dependency to that. This issue is intended to track that update.