Fixes audit trail pagination data within list endpoint

[brandonc]

Closes #585

Description

The Audit Trails endpoint is a bit of a snowflake and uses different keys than what was conventional. Added test coverage.

External links

Output from tests

Including output from tests may require access to a TFE instance. Ignore this section if you have no environment to test against.

go test ./... -v -run TestAuditTrailsList
=== RUN   TestAuditTrailsList
=== RUN   TestAuditTrailsList/with_no_specified_timeframe
=== RUN   TestAuditTrailsList/with_no_specified_timeframe/pagination_parameters
=== RUN   TestAuditTrailsList/with_no_specified_timeframe/with_resource_deserialized_correctly
=== RUN   TestAuditTrailsList/with_no_specified_timeframe/with_auth_deserialized_correctly
=== RUN   TestAuditTrailsList/with_no_specified_timeframe/with_request_deserialized_correctly
=== RUN   TestAuditTrailsList/using_since_query_param
--- PASS: TestAuditTrailsList (12.45s)
    --- PASS: TestAuditTrailsList/with_no_specified_timeframe (1.32s)
        --- PASS: TestAuditTrailsList/with_no_specified_timeframe/pagination_parameters (0.76s)
        --- PASS: TestAuditTrailsList/with_no_specified_timeframe/with_resource_deserialized_correctly (0.00s)
        --- PASS: TestAuditTrailsList/with_no_specified_timeframe/with_auth_deserialized_correctly (0.00s)
        --- PASS: TestAuditTrailsList/with_no_specified_timeframe/with_request_deserialized_correctly (0.00s)
    --- PASS: TestAuditTrailsList/using_since_query_param (2.60s)
PASS
ok  	github.com/hashicorp/go-tfe	13.245s
?   	github.com/hashicorp/go-tfe/examples/organizations	[no test files]
?   	github.com/hashicorp/go-tfe/examples/workspaces	[no test files]
?   	github.com/hashicorp/go-tfe/internal/testsetup	[no test files]
?   	github.com/hashicorp/go-tfe/mocks	[no test files]
...

[sebasslash]

Subtle catch, thanks for this fix 🔥

[github-actions]

Reminder to the contributor that merged this PR: if your changes have added important functionality or fixed a relevant bug, open a follow-up PR to update CHANGELOG.md with a note on your changes.