chore: updated all names from original github to new gitlab location

.github/ISSUE_TEMPLATE/config.yml

CHANGES.md

CONTRIBUTING.md

PULL_REQUEST_TEMPLATE.md

README.md

UPGRADE.md

advanced-examples/custom-http-client.md

client/client.go

client/client_test.go

client/error_test.go

client/jwt/access_token.go

client/jwt/jwt.go

client/jwt/jwt_test.go

client/jwt/taskrouter/capability_token.go

client/request_handler_test.go

client/unmarshal_test.go

cluster_test.go

go.mod

rest/accounts/v1/api_service.go

rest/accounts/v1/credentials_aws.go