[release/4.x] d/aws_s3_object: Test key with leading ./

[ewbankkit]

Description

S3 objects keys with a leading "dot slash" (./) have those characters removed by AWS SDK for Go v1.
Test this.

Output from Acceptance Testing

% make testacc TESTARGS='-run=TestAccS3ObjectDataSource_leadingDotSlash' PKG=s3
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/s3/... -v -count 1 -parallel 20  -run=TestAccS3ObjectDataSource_leadingDotSlash -timeout 180m
=== RUN   TestAccS3ObjectDataSource_leadingDotSlash
=== PAUSE TestAccS3ObjectDataSource_leadingDotSlash
=== CONT  TestAccS3ObjectDataSource_leadingDotSlash
--- PASS: TestAccS3ObjectDataSource_leadingDotSlash (35.99s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/s3	41.579s

[github-actions]

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[github-actions]

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